Sky & telescope australian may 2014 by sangsangsau

Saturn: SEE TERBY’S WHITE SPOT p.66

Science: WHAT HAPPENED TO COMET ISON? p.32

Why Is Our Galaxy Blowing Bubbles? p.38

Observing: GOING DEEP IN M83 p.74

FREE Sta

r Chart Offer! p.7 7

THE ESSENTIAL MAGAZINE OF ASTRONOMY MAY/JUNE 2014

Cosmos Reborn

Neil Tyson remakes Sagan’s TV classic p.22 TEST REPORT: iOptron’s Radically Different Telescope Mount p.44 HOW TO: Enhance Your Nebula Images p.82

LESS IS MORE: Happiness with a Simple Scope p.78

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May/June 2014 Vol. 10, No. 4

Contents p.22

The Ship of the Imagination returns

NEWS & FEATURES 10 Spectrum Astronomy Reaches Out By Greg Bryant 12 t t t t

News Notes .JTTJOH (BMBYZ $MVTUFST (BJB -BVODIFT .POTUFS #VSTU $IBMMFOHFT Ä&#x2021;FPSJFT BOE NPSFy

18 5 Years Ago By Greg Bryant 19 Spotlight On ... )VCCMF 5VSOT 20 Discoveries $MFBSJOH UIF 7JFX UP UIF 4UBST By David Ellyard

Cover Story 22

The Return of Cosmos 8JMM UIJT IJHI QSPÄ&#x2022;MF CJH CVEHFU UFMFWJTJPO TFSJFT BCPVU UIF VOJWFSTF CF B XPSUIZ TVDDFTTPS UP JUT HSPVOECSFBLJOH QSFEFDFTTPS By J. Kelly Beatty

ISONâ&#x20AC;&#x2122;s Day in the Sun .BZCF JU XBTO U UIF QVCMJD T $PNFU PG UIF $FOUVSZ CVU GPS BVUIPS ,BSM #BUUBNT JU XBT IJT $PNFU PG UIF $FOUVSZ By Karl Battams

Mystery in the Milky Way 5XP HJHBOUJD CVCCMFT FKFDUFE GSPN PVS HBMBYZ T DFOUSF MBVODIFE BTUSPOPNFST PO B EFDBEF MPOH PEZTTFZ By Camille M. Carlisle

p.38

Bubbles in the Milky Way

p.32

AS&T TEST REPORT 44 iOptronâ&#x20AC;&#x2122;s New ZEQ25GT Mount Ä&#x2021;FSF T NPSF UP UIJT &RVBUPSJBM (P 5P NPVOU UIBO KVTU B SBEJDBM OFX EFTJHO By Dennis di Cicco 48 New Product Showcase

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A Chronicle of Comet ISON

p.91

p.82

Inspiring images from our readers

Improve your astroimages

OBSERVING & EXPLORING 49 In This Section

THE ASTRONOMY SCENE 50 Binocular Highlight Near and Far in Coma Berenices By Gary Seronik 52 Tonight’s Sky Splendid Spica By Fred Schaaf 54 Sun, Moon, and Planets Saturn Shines All Night By Greg Bryant 60 Celestial Calendar Saturn Double Header By Steve Kerr 61 Celestial Calendar Prospects for a Near-Earth Comet By David Seargent 63 Celestial Calendar AH Scorpii By Alan Plummer 64 Exploring The Moon History of the Moon By Charles A. Wood 66 Exploring The Solar System When Seeing Isn’t Believing By Thomas Dobbins 68 Double Star Notes The Crab and The Beehive By Ross Gould 70 Targets The Ghost of Jupiter By Sue French 74 Going Deep Digging Deep in Messier 83 By Steve Gottlieb

76 Telescope Workshop The Jones Medial Refractor By Gary Seronik 78 Stargazing Simpliﬁed A small scope at medium-low power has boundless potential. By James Mullaney 82 Red Luminance Layering Boost the nebulosity in your astrophotos with this novel technique. By Edward Henry 86 Observing Project Why do I Observe Lunar Occultations? By Peter Anderson 88 A 70-inch Amateur Telescope This monster Dob is likely the largest transportable amateur scope in the world. By Chuck Hards

p.78

Small scope, big view

ON THE COVER A new version of the iconic TV series returns, aiming to inspire the next generation as its predecessor did. SPIRAL GALAXY: NASA ⁄ ESA ⁄ THE HUBBLE HERITAGE TEAM (STSCI ⁄ AURA); NEIL TYSON: PATRICK ECCLESINE ⁄ FOX

32 66

74 38

91 Gallery 96 Index to Advertisers 97 Manufacturer and Dealer Directory 98 Focal Point How the Web Saved the Webb By Nick Howes

SUBSCRIBE TO AS&T 77 Subscription Offer Subscribe and receive a Star Charts CD!

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22 44 82 78 AUSTRALIAN SKY & TELESCOPE (ISSN 1832-0457) is published 8 times per year by Odysseus Publishing Pty Limited, PO Box 81, St Leonards, NSW, 1590. Phone (02) 9439 1955, fax (02) 9439 1977. © 2014 Odysseus Publishing Pty Limited. All rights reserved.

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Greg Bryant Spectrum THE ESSENTIAL MAGAZINE OF ASTRONOMY ISSUE NO 77 MAY/JUNE 2014

Astronomy Reaches Out

EDITORIAL EDITOR Greg Bryant DESIGN Simone Marinkovic CONTRIBUTING EDITORS John Drummond, David Ellyard, Ross Gould, Steve Kerr, Steve Lee, Alan Plummer, David Seargent EMAIL info@skyandtelescope.com.au

Make the most of what’s on offer.

ADVERTISING ADVERTISING MANAGER Greg Bryant EMAIL greg@skyandtelescope.com.au

s a kid, I remember watching the late Carl Sagan enchant us with the marvels of the universe through his TV series Cosmos. He would later be in the spotlight again through his work for The Planetary Society and his books such as Contact (which was being made into a movie, starring Jodie Foster, around the time of his death in 1996), but it was through Cosmos that he help explain the universe to so many people. Now, in true entertainment fashion, it’s been rebooted. Neil Tyson, an astronomy populariser well know in the United States, is a great choice to host the updated series. It’s being broadcast here in Australia on the National Geographic channel. I’ve seen the first few episodes and he comes across very well. ... and if you’re unable to watch it on National Geographic (and I’m sure it will be repeated), there’s no doubt the box set will be available soon! These days, it’s great to see so many astronomy documentaries on television. Finally, I want to mention the Gemini Observatory Contest — the opportunity to select an object to be imaged with the 8-metre Gemini South Telescope in Chile. As with last year, there are 2 divisions, one for Australian school students in years 5 – 12 and one for Australian amateur astronomers. The Australian Gemini Office has run this competition since 2009, initially just for school students, and there have been some great images that have come out of it. The closing date for entries is fast approaching — 10 May. This year sees the AAO’s Fred Watson joining the judging panel for the contest. The resulting images from the winning submissions will be published in Australian Sky & Telescope magazine. For more information, including tips on what to consider when choosing a target to enter in the competition, visit http://ausgo.aao.gov.au/contest/

SUBSCRIPTION SERVICES TEL 02 9439 1955 EMAIL subs@odysseus.com.au ODYSSEUS PUBLISHING PTY LIMITED ABN 39 122 001 665 TEL 02 9439 1955 FAX 02 9439 1977 ADDRESS Suite 15, Level 2/174 Willoughby Road, Crows Nest NSW 2065 PO Box 81, St Leonards, NSW, 1590 PUBLISHERS Ian Brooks and Todd Cole Printed by Webstar Approximately 6,000 light-years from us, the Gum 85 nebula in Serpens surrounds the open cluster NGC 6604. This was the winning image in the student division of last year's Gemini Observatory Contest. PAUL FITZGERALD (IVANHOE GIRLS GRAMMAR SCHOOL SCHOOL) / TRAVIS RECTOR (UNIVERSITY OF ALASKA ANCHORAGE) / AUSTRALIAN GEMINI OFFICE

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EDITORIAL SENIOR EDITORS Dennis di Cicco, Alan M. MacRobert ASSOCIATE EDITOR Tony Flanders IMAGING EDITOR Sean Walker ASSISTANT EDITOR Camille M. Carlisle WEB EDITOR Monica Young EDITOR EMERITUS Richard Tresch Fienberg SENIOR CONTRIBUTING EDITORS J. Kelly Beatty, Roger W. Sinnott DESIGN DIRECTOR Patricia Gillis-Coppola ILLUSTRATION DIRECTOR Gregg Dinderman Founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer

NGC3576. ProLine camera with 2048 x 2048 back-illuminated sensor. Telescope Design: Philipp Keller. Image courtesy of Wolfgang Promper.

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News Notes

COSMOLOGY I

Missing Galaxy Clusters

The young, massive cluster ICDS J1426.5+3508 contains the mass of as many as 500 trillion Suns. It’s rarer than it should be: Astronomers haven’t found as many galaxy clusters in the universe as they expected to. NASA / ESA / A. GONZALEZ (UNIV. OF FLORIDA) / A. STANFORD (UC DAVIS AND LLNL) / M. BRODWIN (UNIV. OF MISSOURIKANSAS CITY AND HARVARDSMITHSONIAN CFA)A

stronomers have counted the number of galaxy clusters in the cosmos and found a problem: there aren’t enough of them. Galaxy clusters are essentially big lumps in the distribution of matter in the universe. The lumpiness they reveal grew from matter’s lumpiness in the primordial universe, which we see preserved in the minuscule temperature fluctuations in the cosmic microwave background (CMB). With the right theoretical model, astronomers should be able to match up the two sets of observations, explains David Spergel (Princeton). But as researchers reported at the January American Astronomical Society meeting, it’s not proving that easy. James Bartlett (JPL and APC Université Paris Diderot-Paris 7, France) presented a map of 189 galaxy clusters based on the “shadows” these clusters leave in the CMB as observed by ESA’s Planck spacecraft. The number of galaxy clusters found using this shadow method matches those tallied using X-ray and

12 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

optical surveys. But it doesn’t match what researchers predict based on the clumpiness in the CMB. In fact, as Brad Benson (Fermilab and the University of Chicago) explained in a subsequent talk, the CMB as seen by Planck suggests that the universe should have 2.5 times more galaxy clusters than astronomers actually observe. His team’s preliminary analysis of about 300 clusters’ shadows in data from the South Pole Telescope also conflicts with Planck’s CMB-based cosmology. There are several potential explanations. One, the tension might not actually be there. If the masses calculated for clusters are too low by a factor of about 1.4, that would resolve the issue. Astronomers often calculate a cluster’s mass by extrapolating from its X-ray luminosity, and the assumptions involved might be off. But masses calculated using X-rays and weak gravitational lensing are consistent within about 10 to 15% of each other, Benson says. The chances of the measurements being off enough

to match CMB predictions are less than 1 in 300 at best. Two, neutrinos might be to blame. Scientists know the particles have some tiny yet still-undetermined mass. Neutrinos four to five times heavier than the lower limit calculated from experiments could erase the problem. Some researchers are currently pursuing this solution. Three, perhaps scientists’ analysis of the CMB temperature map is off, and the primordial matter fluctuations aren’t as strong as the Planck team proposes. An independent analysis by Spergel’s team suggests such could be the case. Or maybe something else is going on. “This is, I think, a wonderful situation,” Spergel said at the meeting. In the next year or two, astronomers will either have evidence for new physics or have done away with the tension, he explained. “It’s an exciting moment.” CAMILLE M. CARLISLE

News Notes

STELLAR I Monster Burst Challenges Theories Collision-induced shock waves create radiation Forming black hole

Jet

Dying star

NASA GSFC

Observations of one of the most powerful exploding stars ever recorded suggest that the standard model for gamma-ray bursts might be missing a piece of the puzzle, scientists report in papers published online November 21st in Science. The gamma-ray burst GRB 130427A set off an alarm on NASA’s Fermi Gamma-ray Space Telescope on April 27, 2013. The Swift spacecraft, an array of ground-based robotic telescopes called RAPTOR, the CARMA millimetre-wave observatory, and NASA’s NuSTAR X-ray telescope also joined in on the action. In the end, the explosion flooded 58 ground- and spacebased observatories with its photons.

These observations show that GRB 130427A is the longest, most energetic explosion on record. While the main burst lasted just 20 seconds (a typical duration for this kind of “long” GRB), stray gamma rays kept pouring in for another 20 hours. Two of the thousands of gamma-ray photons Fermi collected during that time are problematic. The first appeared 19 seconds after the burst began; the next appeared 3¾ minutes later. Both packed a serious punch: 73 and 95 billion electron volts, the highest-energy photons ever recorded from a GRB. According to the current scenario, these photons shouldn’t have existed. In the

MISSIONS I Gaia Launches to Pinpoint a Billion Stars

This illustration depicts the Gaia spacecraft in deep space, hard at work mapping 3-D locations for many of the Milky Way’s stars. SPACECRAFT: ESA / ATG MEDIA LAB; BACKGROUND: ESO / SERGE BRUNIER

14 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

standard picture, long GRBs like 130427A herald the collapse of very massive stars. As the star’s core implodes to create a black hole, a jet forms and burns its way through the star’s outer layers in seconds. The jet then rams into the surrounding gas cocoon left behind by the dead star’s winds, pushing electrons to relativistic speeds which race through surrounding magnetic fields, releasing their pent-up energy as synchrotron radiation. But no matter how fast these electrons spiral, they can’t radiate away the 73 billion and 95 billion electron volts the two photons carried. One study’s lead author, Alessandro Maselli (INAF-IASF Palermo, Italy), suggests that the same electrons that created the photons in the first place could pass on an extra punch of energy if they later collide with their progeny. But a coauthor on another study, Charles Dermer (Naval Research Laboratory), says that if the GRB made its photons in two different ways, we should see a jump in the number created at different energies (for example, many more gamma rays than X-rays). Instead, the whole spectrum from visible light to ultrahigh-energy gamma rays is smooth, suggesting all the photons come from one mechanism. The teams propose everything from snapping magnetic field lines to scorchinghot gas around the forming black hole as solutions. They haven’t ruled out the synchrotron model, but it’s clear that something extra is needed. MONICA YOUNG

ESA’s long-awaited Gaia mission launched December 19th on a Soyuz rocket from Europe’s spaceport in Kourou, French Guiana. The spacecraft’s instruments will map the size, shape, and dynamics of our galaxy to extraordinary precision by obtaining über-accurate star positions, motions, and distances. Accurate star positions are the foundation of nearly everything we know about stars and, in turn, form the base for the cosmic distance scale. Gaia is the first great leap in the measurement of stellar positions, proper motions, and parallaxes — called astrometry — since ESA’s Hipparcos mission of the early 1990s. The plan is to map 1 billion stars down to 20th magnitude, nearly 1% of all the stars in our galaxy. Gaia will measure stars from 5th to 15th magnitude to an accuracy of at least 25 microarcseconds, and even better on the brighter end of this range. That’s 40 times

News Notes

more precise than Hipparcos could do for stars down to magnitude 8 or 9. Gaia will measure its faintest stars (to magnitude 20) to 300 microarcseconds or better. It will also catalogue star brightnesses from the near ultraviolet to the near infrared (AS&T: May/ June 2008, page 34). To accomplish these feats, Gaia will observe each star about 70 times. Additionally, it will measure the stars’ radial velocities, creating a full 3-D map of both their motions and locations. The accuracy of individual parallaxes will range from 20% for stars near the galactic centre (26,000

light-years away) to a remarkable 0.001% for nearby dim stars. Gaia will carry out its planned 5-year mission at the Sun-Earth L2 Lagrangian point, 1.5 million kilometres away from our planet’s nightside. The spacecraft’s two identical telescopes point 106.5° apart, and as the craft rotates once every 6 hours, each will survey a narrow band of the celestial sphere. A gradual tilt of the spacecraft’s axis will slowly result in full-sky coverage. The telescopes have folded focal lengths of 35 metres and focus onto imaging chips totalling more than 900 megapixels. Gaia is

expected to produce more imaging data in 5 years than NASA’s Hubble Space Telescope did in its first 21 years. Ultimately, Gaia should produce topquality 3-D coordinates for 10 million stars, compared with Hipparcos’s 118,000 measured stellar parallaxes. The first catalogues should come in mid-2016 and the final one around 2023. Gaia’s mission planners also hope to gather indirect data on hundreds of exoplanets and possibly identify thousands of new brown dwarfs. EMILY POORE & ALAN M. MACROBERT

BLACK HOLES I Galactic Runts Host Beasts

Three years ago, astronomers stumbled across a massive black hole in the dwarf galaxy Henize 2-10, pictured here in a composite optical, radio, and X-ray image. The ﬁnd led to a more widespread search for massive black holes in 25,000 dwarf galaxies. X-RAY: NASA / CXC / VIRGINIA / AMY REINES ET AL; RADIO: NRAO / AUI / NSF; OPTICAL: NASA / STSCI

Astronomers are edging closer to discovering how the universe’s most massive black holes form — by studying the smallest galaxies. It’s easy to make a black hole a few times the mass of the Sun: a massive star loses its battle against gravity and collapses under its own weight. But no star contains millions or even billions of Suns, which is where the most massive black holes weigh in. There are two main ideas on how to grow these monsters. One camp holds that supermassive black holes could be the remnants of the first generation of stars. Unpolluted by heavier elements, these stars could have grown to tremendous sizes, with masses up to hundreds of times that of the Sun. These stars then would have collapsed into “seed” black holes that then grew to supermassive sizes by sucking in more material. Even better, says another camp, would be to collapse a black hole directly out of

a gas cloud. That’s tricky to do, but with the right conditions it might be possible to make black holes thousands of times the mass of the Sun. Observers have detected black holes a billion times the mass of the Sun just 1 billion years after the Big Bang, so this theory is a tempting one. To find the answer, astronomers are looking at dwarf galaxies. Dwarfs haven’t changed much since the beginning of the universe, so they should retain the memory of black holes’ seeding scenario, says Amy Reines (NRAO). If supermassive black holes formed from the first stars, then every dwarf should have one. On the other hand, because the direct-collapse process is more difficult, it would probably leave most dwarf galaxies without a supermassive black hole to call their own. Until recently, astronomers had only found a few cosmic heavyweights in dwarf galaxies, such as the one in NGC 4395, which is a few hundred thousand times the mass of the Sun.

16 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

Reines and her colleagues have expanded that sample. Presenting at the January AAS meeting, Reines’s team pulled 25,000 dwarf galaxies from the Sloan Digital Sky Survey and searched their visible-light spectra for telltale signs of a massive, feeding black hole. They found those signals in 151 dwarf galaxies — not even 1% of the full sample. Reines cautions that this result is only a first step, because the team could only detect feeding black holes. Dormant ones — and most of these objects would be dormant most of the time — would go undetected, and a dwarf galaxy with lots of star formation would drown out its own black hole signal. The team next plans to observe with the Very Large Array and NASA’s Chandra X-ray Observatory. Black holes emit in radio and X-rays even when not chowing down, so the expanded survey should reveal quieter beasts that are invisible to SDSS. MONICA YOUNG

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News Notes

GALAXIES | NGC 5824: A Stripped Dwarf Galaxy? Our understanding of globular clusters, the night sky’s stellar cities, has grown in leaps and bounds in recent decades. In that time, we’ve come to realise that Omega Centauri and M54 are not true globular clusters — they’re the core remnants of dwarf galaxies that have been stripped by our Milky Way. There are a few other globulars for whom questions have been raised too. Now another suspected dwarf galaxy core can be added to the list: NGC 5824, a catalogued 9th magnitude globular cluster in Lupus. In a study published in Monthly Notices of the Royal Astronomical Society in March, Gary Da Costa (Australian National University) and colleagues measured the chemical abundances of 90 red giants in NGC 5824, using spectra taken with the Very Large Telescope and the Gemini South Telescope in Chile, and found a wide range of values, in contrast to the normal tight range for globulars, but consistent in distribution with what has been observed for Omega Centauri and M54.

Glowing at 9th magnitude, NGC 5824 is now suspected of being the core remains of a dwarf galaxy captured by our Milky Way. DSS

NGC 5824 was also found to be surrounded by a diffuse stellar envelope, perhaps the remnants of a dwarf galaxy of which NGC 5824 was the core stellar cluster, and there appears to be a connection with a stream of stars known as the Cetus Polar Stream. Further deep studies of NGC 5824 are being conducted by the team. GREG BRYANT

5 Years Ago May/June 2009

Exoplanet Hothead If you’re fascinated by weather extremes — tornadoes, hurricanes — you’d probably like the weather on HD 80806b. This massive hot Jupiter swings in a very elongated orbit (eccentricity 0.93) that sends it diving, every 111 days, to within just 5 million kilometres of its Sun-like star. During one recent swingby, astronomers using the Spitzer Space Telescope detected the planet’s infrared glow — and found that its temperatures rose by nearly 700oC in just six hours. This was the first detection of weather changes in real time on a planet outside our solar system.

The 1st Earth-Size Exoplanet The international team of astronomers on the French-led CoRoT (Convection, Rotation, and planetary Transits) mission announced the discovery of CoRoT-Exo-7b, a transiting exoplanet with a radius only about 1.7 times that of Earth. This newfound planet orbits TYC 4799-1733-1, a 12th magnitude K0 dwarf in Monoceros. The planet goes around the star in an astoundingly short 20.5 hours. This is the first exoplanet orbiting a normal star that we can confidently classify as “terrestrial”.

Astro Calendar National Australian Convention of Amateur Astronomers 18 – 21 April Rydges Bell City, Preston, Vic Biennual convention for amateur astronomers, hosted this year by the Astronomical Society of Victoria www.nacaa.org.au South Pacific Star Party 22 – 25 May Ilford, New South Wales Annual star party, hosted by the Astronomical Society of New South Wales www.asnsw.com/spsp RASNZ Conference 2014 6 – 8 June Whakatane, New Zealand Annual conference of the Royal Astronomical Society of New Zealand www.rasnz.org.nz CWAS Astrofest 12 – 13 July Parkes, NSW Annual conference incorporating the David Malin Awards www.cwas.org.au/astrofest/ Queensland Astrofest 18 – 27 July Lions Camp Duckadang, Linville, Qld Long-running annual star party www.qldastrofest.org.au Border Stargaze 23 – 26 October Great Aussie Holiday Park, near AlburyWodonga, NSW Annual star party hosted by the Astronomical Society of AlburyWodonga www.asaw.org.au VicSouth Desert Spring Star Party 24 – 27 October Little Desert Nature Lodge, Nhill, Vic Annual star party hosted by the astronomical societies of Victoria and South Australia www.vicsouth.info WHAT’S GOING ON?

The CoRoT mission ended in 2012. Author Brandon Tingley, who did his PhD at Mt Stromlo Observatory (ANU), was a member of the CoRoT science team. 18 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

Do you have an event or activity coming up? Email us at greg@skyandtelescope.com.au.

Spotlight On

he Hubble Space Telescope celebrated its 24th year in orbit on 24 April (last monthâ&#x20AC;&#x2122;s issue, page 20), and to mark the occasion, scientists released this infrared image taken with Hubble in early February of a portion of the nebula NGC 2174, also catalogued as Sharpless Sh2-252 and just popularly known as the Monkey Head Nebula. Lying some 6,000 light-years from us in the constellation Orion (about four times farther away than the Great Orion Nebula), NGC 2174 is a vast region of starbirth with young stars embedded within clouds of gas and dust.

ABOVE: The ultraviolet light from newly formed stars carves up the dust in this Hubble Space Telescope image. RIGHT: The position of Hubble's infrared image is seen in a wider view of the nebula captured by amateur astronomer Richard Crisp. NASA / ESA / HUBBLE HERITAGE TEAM / R. CRISP

â&#x20AC;&#x201C; GREG BRYANT

www.skyandtelescope.com.au 19

David Ellyard Discoveries

Clearing the View to the Stars Sometimes patents aren’t awarded to the discoverer...

n 8 June 1758, London-based optician John Dollond announced to the Royal Society a discovery that would transform the working lives of astronomers (as well as of biologists). By that time telescopes and microscopes had been aiding researchers for a century and half, vastly expanding our knowledge of the Universe beyond the Earth, as well as revealing an unsuspected “microcosm” of living things too small to be seen with the unaided eye. At the start there were problems making glass pure enough for highquality lenses for such instruments and even the best lenses had another problem — the images were surrounded by coloured fringes. Such “chromatic aberration” made details hard to discern. The solution that Dollond offered, based on the experiments he reported to the Royal Society, involved a “doublet”, two lenses of different shapes and made of different types of glass cemented together. A convex lens of “crown glass”, united with a lens of “flint glass”, concave on one side, flat on the other, suppressed the chromatic aberration, leaving the images free of unwanted colour. Dollond, son of a Huguenot silk weaver from East London and who had set himself up with his son Peter as a maker of optical instruments in 1752, did well from his invention, for which he was granted a patent. He gained the gratitude of observers, as well as the Copley Medal from the Royal Society. He was a Fellow two years later and made Optician to the King. As is commonly the case in science and technology, that is not the whole story. Although Dollond had his patent and the public recognition, the discovery was not originally his. At least two other people had a hand in it. The story begins with Isaac Newton. More than fifty years before Dollond, Newton had discovered that white light was a mixture of colours, from red to violet, and these colours are separated (“dispersed”) when a ray of light is bent

(“refracted”) by passing through a lens or prism. As a result, each colour of light was brought to a slightly different focus by a lens, producing a number of superimposed images in different colours. Hence the “fringes”. Newton thought this problem was inherent in lenses and could not be fixed. That led him to pioneer the “reflecting telescope”, which used a mirror rather than a lens to collect and concentrate light from celestial objects. But other people thought a solution was possible. After all, the human eye produces images free of such aberration. Perhaps the different “humours” in the eye combine to so refract rays of light as to produce an image on the retina without added colour. So perhaps combining lenses made from different materials might do the same. These would disperse light by different amounts and if properly arranged could cancel out the effect. Such lenses would be “achromatic” (“without colour”). One who thought so was Chester Moor Hall, a lawyer and amateur optician living in Essex. His first experiments combined solid glass lenses

20 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

John Dollond, portrayed here in this 18th century painting, successfully commercialised the achromatic doublet, which led to improved optical images. BENJAMIN WILSON

with lenses filled with water. He soon moved onto a more practical arrangement combining lenses of different compositions (crown glass and flint glass; the latter containing lead oxide). By around 1730 he had used his discovery to build a refracting telescope free of chromatic aberration, something Newton had thought impossible. He seems to have kept the idea very much to himself, but the secret was uncovered by London optician George Bass, who had been contracted (through intermediaries) to make the crown and flint glass components to the doublets. Putting them together he soon realised their significance, but the secret was not his to make public. The discovery remained little known for another quarter of a century, until Bass passed it on to Dollond. Dollond was at first sceptical, since the idea seem to conflict with the mighty Newton. Experiment soon convinced him otherwise, and the immense possibilities of the discovery for improving both telescopes and microscopes were immediately apparent. The announcement to the Royal Society and the patent application quickly followed, and Dollond went into production. Dollond was naturally well aware of the previous work; even though he had been granted a patent he chose not to enforce it. Others began to make the achromatic doublets. Not till after the elder Dollond died in 1761 did his son Peter take action against those who had infringed. The matter went to court; much of the background emerged during proceedings. The Dollond patent was upheld, on the grounds that he had made “productive use” of the discovery whereas others had not. Every astronomer and microscopist makes productive use of it now. ✦ David Ellyard presented SkyWatch on ABC TV in the 1980s. His StarWatch StarWheel has sold over 100,000 copies.

TV Odyssey

The Return of

COSMOS Will this high-proﬁle, big-budget television series about the universe be a worthy successor to its groundbreaking predecessor?

ay back in 1980, Cornell astronomer Carl Sagan and public television’s KCET in Los Angeles teamed up to produce 13 hours of prime-time programming about the universe and everything therein. Cosmos: A Personal Voyage was an audacious undertaking at a time when American audiences were still getting used to cable television. Sagan strove to be “engrossing and captivating to a broad, general audience, while simultaneously portraying science accurately and even conveying something of what makes it tick.” Filmed on 100 locations worldwide and infused with state-of-the-art special effects, Cosmos was a smash hit. It has been seen by an estimated 800 million viewers worldwide, making it the Public Broadcast System’s mostwatched series of all time. It made Sagan an iconic figure, more celebrity than scientist in the minds of many. And his captivating style and powerful narration helped propel astronomy to new levels of “cool.”

J. KELLY BEATTY

22 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

Now consider what Sagan, together with cowriters Ann Druyan (whom he later married) and astronomer Steven Soter, couldn’t show their viewers: Voyager 2 had yet to reach Uranus or Neptune. The Hubble Space Telescope was still 10 years from launch. The concept of dark energy was decades away. Not a single extrasolar planet had been discovered. Sadly, Sagan died in 1996, at just 62, after a difficult, years-long battle with myelodysplasia. Druyan resolved to keep his drive for scientific literacy and enlightenment alive. About six years ago she and Soter got serious about rolling out a completely retooled “Cosmos 2.0,” with astrophysicist Neil DeGrasse Tyson, the irrepressible director of New York’s Hayden Planetarium, serving as host and cosmic tour guide. But the usual cable and public television outlets weren’t biting. Programs such as the History Channel’s The Universe and BBC’s Wonders of the Universe, to name just two, had already

been providing TV viewers with a steady diet of prime-time astronomy. Then one evening in 2011, after speaking at an event in Los Angeles, Tyson was approached by entertainment wunderkind Seth MacFarlane. He was eager to champion astronomical outreach — after all, MacFarlane gushed, Sagan and Druyan’s work had been a huge influence as he grew up. Before long, MacFarlane and Druyan were pitching Cosmos to Peter Rice, head of Fox Broadcasting, and wowing him. It’s been a race to the finish line ever since. Beginning Sunday evening, March 16th, Cosmos: A SpaceTime Odyssey is being broadcast on the National Geographic Channel here in Australia (having begun a week earlier on the Fox television network in the United States). All told, it will debut in 174 countries and 47 languages — arguably the most globalised rollout of any series in television history. Expect repeats too. Fox executives wouldn’t divulge the project’s cost, but it must be

The Ship of the Imagination (SOTI) explores the murky realm inside one of Titan’s many lakes. SOTI appears in all 13 episodes of Cosmos: A SpaceTime Odyssey. SOTI ILLUSTRATION COURTESY FOX.

astronomical. The series is being produced jointly by Druyan’s Cosmos Studios and MacFarlane’s Fuzzy Door Productions. They’re joined by veteran television executive Mitchell Cannold and Emmy-nominee Brannon Braga as executive producers. Braga is also the series’ director. Bill Pope (of Matrix fame) directed the photography, and Rainer Gombos (Game of Thrones, The Perfect Storm) leads the special-effects team. MacFarlane’s production company supplied the animation sequences — more on that later — voiced by A-list actors such as Kirsten Dunst, Amanda Seyfried, and Patrick Stewart.

Prime-Time Astronomy With that kind of entertainment firepower, can the series deliver content that’s captivating enough to hold viewers’ interest for 13 weeks? “We’re telling completely new, untold stories,” Druyan responds. More importantly, it’s not just an astronomical romp across the universe. “It’s about geology,

climate, biology, cosmology, chemistry, engineering, and mathematics.” “Cosmos is a series that very much covers the whole breadth of science,” agrees Cannold, who got hooked on astronomy at a young age (and who is a longtime reader of S&T). “From first moment to last, viewers feel they’re on an adventure from the get-go, and they’ll want to come back every week.” The production has been cloaked in secrecy — for example, the shooting locations haven’t been revealed. (One exception: windswept cliffs overlooking the Pacific in Carmel, California, are again used for the iconic opening and closing scenes.) But Fox provided preview clips of some episodes to offer a taste of what’s to come. Two key visual elements from the original series are back. One is the “Ship of the Imagination,” which transports viewers from the very micro (an atom’s nucleus) to the very macro (the edge of the observable universe). Whereas Sagan’s SOTI was a stylised dandelion of light, its new iteration is a

sleek, bubble-domed sliver of futuristic design. The second returnee is the “Cosmic Calendar.” Sagan used this clever visualisation to compress the entire history of the universe (15 billion years back then, 13.8 billion now) into a single year. By this reckoning, our solar system formed in early September — and humans didn’t make their appearance until the final hour of December 31st. Whereas the original series used actors to re-create many historical scenes, this time MacFarlane wanted animations to tell those stories. But don’t expect cameos from the likes of Family Guy’s irreverent character Stewie. Instead, these are straightforward animated sequences with a “gothic-novel feel,” Cannold explains, infusing “an entirely new vocabulary for telling science history to a global audience.” You’ll see portrayals of a book burning in ancient China, the friendship between Isaac Newton and Edmond Halley, and William Herschel www.skyandtelescope.com.au 23

TV Odyssey telling bedtime stories to his son, John, among many others. The special effects are impressive, as expected. In one sequence, Tysonâ&#x20AC;&#x2122;s SOTI hovers over a seething Sun before racing outward on a tour of the solar system. We dive down with him to the hellish surface of Venus, buzz the Viking landers on Mars, peer into a very dramatic re-creation of Jupiterâ&#x20AC;&#x2122;s Great Red Spot, and â&#x20AC;&#x153;surf â&#x20AC;? the rings of Saturn. (One technical quibble is that the asteroid and Kuiper belts veritably teem with closely spaced objects, a misconception dating back to Star Wars.) In another episode, Tyson visits the supermassive black hole at the Milky Wayâ&#x20AC;&#x2122;s core and, throwing caution and physics to the wind, dares to go in. The SOTI shakes violently amid blazing light as it draws near the black holeâ&#x20AC;&#x2122;s event horizon, and just as itâ&#x20AC;&#x2122;s about to

cross over . . . well, youâ&#x20AC;&#x2122;ll have to watch to see what happens.

Ćł !3Ćł +/0Ćł"+.Ćł Ćł !3Ćł !*!. 0%+* Itâ&#x20AC;&#x2122;s inevitable that many of you will want to compare and contrast the original series with the new one. Thatâ&#x20AC;&#x2122;s valid, but only to a point. â&#x20AC;&#x153;Words like â&#x20AC;&#x2DC;rebootâ&#x20AC;&#x2122; and â&#x20AC;&#x2DC;sequelâ&#x20AC;&#x2122; are misleading,â&#x20AC;? cautions Cannold. The new offering is â&#x20AC;&#x153;utterly faithful to the iconic elements of the original series. But all of the material is new and fresh.â&#x20AC;? The host is likewise â&#x20AC;&#x153;new and fresh.â&#x20AC;? Tyson is the obvious choice, at least for American audiences. Heâ&#x20AC;&#x2122;s an increasingly well-known populariser of all things astronomical. Besides his day job in New York, he has hosted the PBS series Nova Science Now, authored 10 books, appears often on American television, has 1Â˝ million followers on

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ĆŤ ĆŤ â&#x20AC;&#x153;It has been written,â&#x20AC;? note the showâ&#x20AC;&#x2122;s creators, â&#x20AC;&#x153;that most epic tales consist of many stories with one hero. Cosmos is one story with many heroes â&#x20AC;&#x201D; the saga of how the generations of humanity discovered our coordinates in space and time and began to understand natureâ&#x20AC;&#x2122;s laws.â&#x20AC;? Below are synopses of the seriesâ&#x20AC;&#x2122; 13 hour-long episodes.

,%/+ !ĆŤÄ ĆŤÄ&#x2018;ĆŤ . $ĆŤÄ Ä&#x2021; Ä&#x2014; 0 * %*#ĆŤ ,ĆŤ%*ĆŤ0$!ĆŤ %('5ĆŤ 5Ä&#x2DC; Host Neil deGrasse Tyson uses his â&#x20AC;&#x153;Ship of the Imaginationâ&#x20AC;? (SOTI) to introduce us to the mad but cosmically insightful 16th-century priest Giordano Bruno (under tree at left). Then he offers a preview of the Cosmic Calendar, which compresses the universeâ&#x20AC;&#x2122;s 13.8 billion years into a single 12-month span. FOX

24 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

TV Odyssey

Druyan and Soter have kept the writing sparse yet evocative, and Tyson demonstrates that he is indeed a worthy successor to his boyhood hero. Twitter, and even has a weekly radio show about space called Star Talk. Tyson feels an obligation to carry on Sagan’s legacy of educating the public about astronomy. Now 55, he first met Sagan in 1975 while considering where to go to college. Surprisingly, Sagan invited him to Cornell University (in upstate New York) and gave the wideeyed teenager a personal tour of his lab. It didn’t work — Harvard University got the nod — and in the years

thereafter the two crossed paths only a handful of times. Sagan was a hip-looking 46 when Cosmos first aired. He had an easily recognisable but measured delivery. Tyson, by contrast, has a more flamboyant style and envious comedic timing, characteristics that make him much better known among Millennials than among Baby Boomers. Thanks to all his TV face time, Tyson is a polished presenter.

But can he convey the same sense of awe and wonderment that made Sagan a household name? Cannold, who is president of Cosmos Studios, puts it this way: “Neil’s enthusiasm and energy are appropriate for the times, just as Carl’s were for those times. The audience will find that he’s effected a style all his own — an aspect of a kid in a candy store. Neil is very good at conveying the awe, wonder, and magic.” Druyan and Soter have kept the writing sparse yet evocative, and Tyson demonstrates that he is indeed a worthy successor to his boyhood hero. “There are people who remember Carl who’d say I’m assuming his mantle,” Tyson The Cosmic Calendar compresses 13.8 billion years into the span of a single year, starting with the Big Bang (on January 1st) and ending now (December 31st).

FOX

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“The Rivers of Life” Evolution and natural selection have taken life on Earth from basic microbes to the stunning biodiversity we see around us today. But mass extinction events have truncated many branches in the Tree of Life.

“When Knowledge Conquered Fear” Mathematical insights by Newton and Halley made sense of orbital motion and transformed comets from malevolent omens to Rosetta Stones of solar system history.

“Hiding in the Light” We’re transported back in time to witness the emergence of the scientiﬁc method and to explore the intertwined meanings of “light” and “enlightenment” during the past two millennia.

“A Sky Full of Ghosts” Viewers discover how light, time, and gravity combine to distort our perceptions of the visible universe. A motorcycle ride through the Italian countryside is used to demonstrate relativistic motion.

26 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

TV Odyssey

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reflects. â&#x20AC;&#x153;The reality is those are big shoes to fill, so I donâ&#x20AC;&#x2122;t try, because I canâ&#x20AC;&#x2122;t. But I can be a really awesome version of myself.â&#x20AC;? Someone who watches all 13 of the 42-minute-long episodes will see the equivalent of five full-length movies â&#x20AC;&#x201D; completely devoted to science. â&#x20AC;&#x153;At a minimum I want to reignite peopleâ&#x20AC;&#x2122;s curiosity in the natural world,â&#x20AC;? Tyson says. â&#x20AC;&#x153;Our collective goal is that the series empowers you to want to learn more.â&#x20AC;? Given todayâ&#x20AC;&#x2122;s cultural environment, the producers feel thereâ&#x20AC;&#x2122;s much at stake here besides television ratings. â&#x20AC;&#x153;When Cosmos was first broadcast, the attitude toward science was much friendlier,â&#x20AC;? Druyan explains. She regrets that so many people have become uninformed

FOX

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Episode 7 Ä&#x2018;ĆŤ ,.%(ĆŤÄ&#x201A;Ä&#x2C6; Ä&#x2014; $!ĆŤ (! *ĆŤ ++)Ä&#x2DC; Determining the true age of Earth has frustrated scientists for centuries. The answer emerges in the saga of a kid from Iowa who ďŹ nds a foolproof way to determine it â&#x20AC;&#x201D; but who attracts a nemesis along the way.

28 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

Episode 8 Ä&#x2018;ĆŤ 5ĆŤÄ&#x2026; Ä&#x2014; %/0!./ĆŤ+"ĆŤ0$!ĆŤ 1*Ä&#x2DC;ĆŤĆŤ Thereâ&#x20AC;&#x2122;s double meaning here: these â&#x20AC;&#x153;sistersâ&#x20AC;? are not only the stars that ďŹ ll the night sky above us but also the pivotal yet largely unsung female astronomers of the early 20th century.

,%/+ !ĆŤÄ&#x160;ĆŤÄ&#x2018;ĆŤ 5ĆŤÄ Ä Ä&#x2014; $!ĆŤ (! 0.% ĆŤ +5Ä&#x2DC; Michael Faraday overcomes the abject poverty he endured as a child to become a scientiďŹ c great whose insights into ďŹ eld theory permeate all the electronic wonders of our modern-day world.

TV Odyssey about and even openly hostile toward factbased thinking, and specifically, climate research. But she senses that the â&#x20AC;&#x153;pendulum is swinging back our way. Weâ&#x20AC;&#x2122;re ready to explore again.â&#x20AC;? Druyan and her dream team promise to offer viewers a â&#x20AC;&#x153;vision of the cosmos on the grandest scale,â&#x20AC;? presenting scientific concepts with â&#x20AC;&#x153;stunning clarity, uniting skepticism and wonder, and weaving rigorous science with the emotional and spiritual into a transcendent experience.â&#x20AC;? Thatâ&#x20AC;&#x2122;s a tall order in this whiz-bang age of seconds-long sound bites and fleeting attention spans. Letâ&#x20AC;&#x2122;s hope they succeed. â&#x153;Ś Senior contributing editor Kelly Beatty also previewed the original Cosmos series in the September 1980 issue of Sky & Telescope. For summaries of those episodes, visit www. tv.com/shows/cosmos/episodes.

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Episode 10 Ä&#x2018;ĆŤ 5ĆŤÄ Ä&#x2030; â&#x20AC;&#x153;The Lost Worlds +"ĆŤ ( *!0ĆŤ .0$Ä&#x2DC; Viewers see their home planet up close and personal, probing its lands, oceans, and all living things â&#x20AC;&#x201D; past, present, and future. Will alien worlds look anything like ours?

,%/+ !ĆŤÄ Ä ĆŤÄ&#x2018;ĆŤ 5ĆŤÄ&#x201A;Ä&#x2020;ĆŤ Ä&#x2014; $!ĆŤ ))+.0 (/Ä&#x2DC;ĆŤ Do we have to die? Do civilizations have an expiration date? Tyson explores our modest attempts to communicate with other intelligent life and introduces us to a spaceship populated by our future descendants.

30 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

,%/+ !ĆŤÄ Ä&#x201A;ĆŤ Ä&#x2018;ĆŤ 1*!ĆŤÄ&#x201A; Ä&#x2014; $!ĆŤ +.( ĆŤ !0ĆŤ .!!Ä&#x2DC; Viewers are reminded that Earthâ&#x20AC;&#x2122;s resources are not boundless and that climate change is a growing threat. Can human resolve and technology combine to save our planet from the fate that befell Venus?

,%/+ !ĆŤÄ Ä&#x192;ĆŤÄ&#x2018;ĆŤ 1*!ĆŤÄ&#x160; Ä&#x2014; * ". % ĆŤ+"ĆŤ0$!ĆŤ .'Ä&#x2DC; Having traveled from the heart of an atom to the farthest reaches of the cosmos, Tyson confronts the realization that we know little about the cosmic ocean into which weâ&#x20AC;&#x2122;ve taken our ďŹ rst, tentative steps.

History Repeats Itself

“I

t can’t do that!” I cried aloud. The date was November 28, 2013, and I had just received new observations of Comet ISON’s brightness as it rounded the Sun. “What is this [mild expletive] comet doing?” The frustration, amazement, and disbelief I experienced that day sum up quite nicely the emotional roller coaster that was the past year or so of my life. Without a doubt it’s been one of the most stressful and intense periods of my career. It has also been the most extraordinary and thrilling. So allow me to walk you through 2013 for a glimpse into how Comet ISON, C/2012 S1,

had me alternating between elation and despair at almost every available opportunity.

In the Beginning In late 2012, the astronomy community was quick to jump on Comet ISON and the potential it held. Three things made this comet stand out. First, it was a surprisingly bright object for being one of the most distant discovered comets on record. Second, it came from the Oort Cloud, an icy reservoir surrounding our solar system and partway to the next nearest star. Third, and the final ingredient in our big bowl of hype-soup, it was following a path that would take it extremely close to the Sun. We were observing a

32 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

dynamically new comet on a sungrazing trajectory that was still more than 16 months from perihelion and already a relatively bright object. This combination wasn’t simply rare; it was unprecedented. Exciting indeed, but here’s where things went somewhat awry early. The astronomy community understandably began speculating on the comet’s prospects, catching the ears of sensationalist media. By November 2012, with ISON still a year from perihelion, a phrase that would come to haunt me — Comet of the Century — began being plastered all over the internet. At this time my professional interest in ISON was already strong, but as yet I had no official involvement in studies of the comet.

The LASCO C3 camera aboard the orbiting Solar and Heliospheric Observatoy (SOHO) kept a dutiful eye on the comet as it rounded the Sun last November 28th.

Nov. 28 - 03:18 UT

Nov. 28 - 12:42 UT

DAMIAN PEACH

Maybe it wasn’t the public’s Comet of the Century, but for author Karl Battams, it was his Comet of the Century.

Above: Comet ISON was a decent photographic object as evident from this November 15, 2013 view. Right: Author Karl Battams helped keep the world informed about ISON’s latest developments.

Nov. 28 - 18:06 UT

Nov. 28 - 23:30 UT

NASA / ESA / SOHO (4)

www.skyandtelescope.com.au 33

History Repeats Itself

As an astrophysicist at the U.S. Naval Research Laboratory, I work with the NASA and ESA solar spacecraft: SOHO, STEREO, and SDO. In January 2013 I was invited to join the NASA-backed Comet ISON Observing Campaign (CIOC). Our mission was to encourage and facilitate a global and celestial observing campaign. The CIOC was high-profile and ambitious, promising extraordinary results, but also hinging on our judgment call that the comet would survive long enough for us to study it. I had never been involved in such an endeavour, but I was assured that it would be fun and not too much work. Despite this being an unfunded effort, I agreed to volunteer my time. After all, it was just a comet. How much time could it possibly take? (Did I not mention my notoriously poor judgment?)

Trouble, Trouble, and More Trouble By March 2013 the campaign was under way, and already there was a problem to deal with — that awful phrase. Even before a dedicated group of professional comet scientists had been set loose on ISON, the media hype machine was already way out of control with talk of the comet being “daytime visible” and “brighter than the Full Moon.” The internet was full of conflicting articles and forum discussion that would either promote grossly exaggerated ideas of the comet’s

performance, or proclaim how we’d set ourselves up to face a Kohoutek-like public-relations disaster. Although ISON held extraordinary scientific potential, it was never likely to be a Comet of the Century. As scientists, we were left in a position where we had to simultaneously tell everyone to not get excited about ISON for the reasons they had heard, but instead get excited for a whole different set of reasons. It was just one of many early and time-consuming challenges that the comet gave us. Well before ISON was encroaching on the inner solar system, it was encroaching on my free time. Hype aside, the professionalastronomy community’s response was overwhelmingly positive. Support for CIOC flooded in from major groundand space-based observatory teams, as well as amateur astronomers equipped with an extraordinary array of advanced instrumentation. Things were shaping up nicely. We just lacked one key element — a cooperative comet. Between April and October 2013, ISON appeared to almost willfully misbehave. In late autumn and through the winter it should have steadily increased in brightness, but instead it remained almost stagnant. There was a small uptick during spring, but given the lofty goals set for ISON, there were definitely hints of an underperformance issue. Compounding the problems were numerous unsubstantiated reports of how the comet was fizzling (it wasn’t),

34 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

Above: Spacecraft as diverse as the Mars Reconnaissance Orbiter and the Hubble Space Telescope captured images of Comet ISON. Hubble’s views include one of the inbound comet (left) amid a ﬁeld of galaxies near the Gemini-Auriga border on April 30, 2013. Hubble’s ﬁnal view (right) was on October 9th when ISON was 280 million kilometres from Earth.

Austrian photographer Gerald Rhemann captured some of the best Earth-based images of the comet, including this one on the morning of November 21st, just a week before perihelion.

and how its nucleus had already fallen apart (it hadn’t). Meanwhile, a vocal minority of conspiracy theorists on the internet were claiming we were withholding information (we weren’t). These were trying times. I was starting to feel a mixture of frustration and panic. I’d just spent the best part of a year telling the world how we were about to get a spectacular amount of data from ISON, but the comet was sputtering along at only a few magnitudes brighter than it was 12 months earlier. But relief, of sorts, was to come.

Nov. 29 - 02:35 UT

Things were shaping up nicely. We just lacked one key element — a cooperative comet. The Brightening Through late October and early November, ISON dramatically increased in both brightness and the rates at which it was releasing dust and gas. It wasn’t yet behaving like a sungrazing comet, but it was at least behaving like a near-Sun comet. It was a start. On November 21st, a healthylooking Comet ISON entered the Heliospheric Imager-1 (HI-1) field of view on NASA’s STEREO-A satellite. This was my domain, and I actually felt happy and relieved for the first time in months. But that feeling persisted for all of 48 hours. ISON’s roller coaster finale was under way, and I awoke on November 25th to bad news — ISON’s dust production rates had gone skyhigh while gas emission had fallen through the floor. This is bad news for a comet, because it implies a massive outburst in which volatiles are exhausted and all trapped dust has been released. An exploding comet would look a lot like this. Its brightness in the STEREO spacecraft images now held the vital clues to its fate, and for this information I turned to my colleague and fellow sungrazer aficionado Matthew Knight. He and I were shoulder to shoulder at Arizona’s Kitt Peak Observatory for perihelion week, and it was there that he gave me more bad news — ISON’s

Nov. 29 - 07:07 UT

Nov. 29 - 12:30 UT

Nov. 29 - 23:32 UT

NASA / ESA / SOHO (4)

www.skyandtelescope.com.au 35

History Repeats Itself

Perihelion: ISON's Last Stand

Pre-perihelion

The digital eyes of Sun-gazing satellites sent most comet watchers on a rollercoaster ride of emotions as ISON swept around the Sun. Although the comet’s pre-perihelion surge in brightness lifted spirits, the mood soon turned sombre as it became obvious the comet’s nucleus did not survive perihelion.

Post-perihelion NASA / ESA / SOHO (2)

brightness had levelled off and was now falling. I believe his quote was, “I think we’ve lost it.” The evidence was almost overwhelming that ISON had fallen apart and was going to fade fast. The mood of the day was sombre. The following three days were a perfect illustration of why part of me never wants to see another comet again, while the rest of me simply can’t wait for the next one. ISON had entered the LASCO C3 field of view on the SOHO satellite, and not only had it decided to stop fading, it was brightening, and

brightening fast. The future was suddenly looking bright. ISON, it seemed, had finally become a sungrazer. Typical comet rules no longer apply here. The surface of the nucleus was not just losing water ice to the vaporising power of sunlight — it was losing everything! Ice and rocks on its surface were being vaporised, and the comet was lighting up accordingly. These were a wonderfully exciting few hours, but there were still surprises to come.

36 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

November 28, 2013. Perihelion day. Bleary-eyed at 4:30 a.m., I trudged through the thin, cold air and total darkness atop Kitt Peak. My first task was to find coffee, and then to find an internet connection that would be my lifeline to both the comet and the outside world throughout what would prove to be the busiest and most amazing day of my career. The first order of business was to look at the LASCO data. By now, the comet was just hours from perihelion and experiencing the most hostile conditions that our solar system could offer a loosely packed snowball. And the latest satellite images painted a grim picture. In this cosmic battle of “Fire vs ISON” (NASA’s rather amusingly titled Google+ hangout I was to attend later that day), it seemed that fire had taken a definite upper hand. Comet ISON was now fading fast. In the hours until perihelion, ISON was truly behaving like the sungrazing comet it was destined to be. At first, this might sound like a good thing because some sungrazers get extremely bright. But there’s something else they also do rather well — fall apart and vaporise. By the time ISON disappeared behind the Sun-blocking disk of the SOHO/ This montage sequence by British astrophotographer Damian Peach follows the development of Comet ISON on (left to right) September 24th, October 11th and 27th, and November 6th, 10th, and 15th. The ﬁrst four views were captured with a 17-inch (43-cm) reﬂector, while the last two were with a 4.2inch (10.7-cm) refractor.

In the following days these dusty remains faded fast and Comet ISON's show was truly over. LASCO C2 camera, we knew what we had just witnessed. We’ve seen it dozens of times before. A long, thin, and dense tail, tapering to a fine needle-like point, told us that Comet ISON was no longer a comet, or at least not in the traditional sense. The intense radiation and shearing gravitational forces of the Sun had obviously proven too much for it.

Phoenix When the comet failed to make any kind of appearance in images from NASA’s Solar Dynamics Observatory, I knew it was over. In 2011, we saw two sungrazing comets in this satellite’s field of view, including the spectacular C/2011 W3 (Lovejoy), so I thought our chances of seeing something this time were good. Even in the scenario of a fully fragmented comet, I thought the debris trail would light up in the Sun’s million-degree atmosphere, leaving a glowing trace across magnetic field lines. But yet again this comet defied my expectations, and the massive cloud of dust and debris passed invisibly through the field of view. Anyone who has watched Hollywood thrillers knows that you can’t just kill the bad guy once and relax. You might think the drama is over, but they never stay down the first time. Although Comet ISON was certainly no bad guy, I admit to making the foolish mistake of assuming the show was over. My heart skipped a beat when “Something has emerged!” (or words to that effect) appeared on my Twitter feed. I could scarcely believe it, but our icy phoenix was emerging from the solar corona. For one more time — albeit truly the final time — Comet ISON made me question every assumption and prediction I had made. Why was it brightening? Maybe there is something still there. I see lots of dust, so surely it must still be producing? A nucleus — there must still be a nucleus! Over the next few hours, as this dusty feature began to brighten, hope clouded my judgment and had me thinking once more that maybe, just maybe, we would get our December comet.

Of course, it was not to be. In hindsight I should have stuck to my initial reaction about the faint and dusty surviving feature. It was clearly not an active object. But I had fallen victim to my own hype, perhaps scarred by trying to guess and doubleguess the behaviour of this extraordinary and dynamic object. Subsequent computer models of the dust tail now provide compelling evidence there was no nucleus and no activity by this time. All that emerged was simply a rubble pile from the object formerly known as Comet ISON, which likely fell apart in the hours and days preceding its brush with the Sun. In the following days these dusty remains faded fast and Comet ISON’s show was truly over. There would be no December sky show, and not even the powerful eyes of the Hubble Space Telescope would give us a parting shot of the comet that had gripped our imagination and attention for well over a year.

Postmortem For many, ISON’s death scene was anticlimactic, leaving only memories and dreams of what could have been. I understand that sentiment, but for me it’s rather different. Beautiful as it is, the focus of my interest is not comets we see in the night sky. Quite the opposite. For me, the interest lies with comets near the Sun, when they are invisible from Earth but shining vividly in spacecraft images. This is a domain rich with science about not only comets but also the Sun and near-Sun conditions. And Comet ISON delivered several days of spectacular images for us to digest and analyse. That analysis is ongoing, and during the coming months and years, numerous scientific papers and results will be announced, detailing the discoveries and insights drawn from this truly amazing event. Although there is so much more I could write here, I think this is the point on which I would like to end. We did not get the Comet of the Century. Comet ISON was never brighter than the Full Moon. It did not

even survive its encounter with the Sun. But we never promised any of that. What we did promise was an allinclusive observing campaign that would result in one of the broadest, largest, and most detailed data sets of any comet in history. Without question, we got this. Within this data lies a wealth of scientific insight that will allow us to carefully piece together the story of Comet ISON, from its formation through to its demise. And this will ultimately allow us to put one more puzzle piece into the big picture of how our solar system and all its amazing contents came to be. Everyone comes away from an event like this with his or her own perspective and opinion, and that’s okay. There’s no right or wrong answer. But for me, both professionally and in many ways personally, this was absolutely my Comet of the Century. Now I’m almost ready for the next one! ✦

This image by Austrian photographer Michael Jäger is one of the last Earth-based views of ISON. It was recorded in the morning twilight of November 22nd with an 80-mm (3.1inch) refractor.

Through his Twitter feed and blog posts on NASA’s Comet ISON Observing Campaign website, astrophysicist Karl Battams kept the world appraised of the comet’s apparition. www.skyandtelescope.com.au 37

Galactic Crime Scene

Mysteryin the

Milky Way

Two gigantic bubbles ejected from our galaxy’s centre launched astronomers on a decade-long odyssey.

villain lurks in our galaxy’s core. Behind the glitter of the Milky Way’s dusty, starstudded plane hides the culprit of one or more ancient upheavals. We don’t know whether it’s the central supermassive black hole or a cascade of stellar explosions. But in the last few million years, something in the galactic centre spewed two gargantuan bubbles of high-speed particles into interstellar space, creating a diffuse dumbbell that spans 50,000 light-years end-to-end. Astronomers have debated the existence of these so-called Fermi bubbles since 2003, when Doug Finkbeiner (now at the Harvard-

CAMILLE M. CARLISLE

This artist’s impression shows the Fermi bubbles (pink) and the Milky Way’s stellar disk (represented by the spiral arms). The bubbles are illustrated to scale. NASA GSFC

38 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

Smithsonian Centre for Astrophysics) discovered a fog of energetic particles in data from NASA’s Wilkinson Microwave Anisotropy Probe (WMAP). But although they’re now accepted as reality, the bubbles still perplex astronomers.

A Curious Mist WMAP might seem an unlikely instrument for a Milky Way discovery. WMAP’s mission was to map the cosmic microwave background (CMB), the leftover radiation from the Big Bang. The spacecraft studied the CMB for nine years in five microwave frequency bands, and its results helped refine modern cosmology. But mapping the microwave background takes more than staring into deep space. The solar system is embedded in the Milky Way’s disk, which means that our galaxy’s glimmering plane stretches across our view of the universe. To look at the CMB, cosmologists first have to identify all the nearby emission sources littering their microwave picture — the bugs on the windshield — and then create maps of the smears so that they can subtract them from the background radiation. While peeling apart layers of WMAP data to look at these bugs for their own sake, Finkbeiner discovered a faint haze in the galaxy’s diffuse microwave emission. The feature extended several thousand light-years above and below the galactic plane before fading into the

background, almost as though something were bleeding out from the core. Most of it was a long-sought signal from spinning dust grains, but there was a residue the dust couldn’t explain. Even as his spinning dust paper was appearing in the Astrophysical Journal, Finkbeiner warily posted another paper on the open-access research site arXiv. org, proposing that the fog might come from dark matter. The haze was synchrotron radiation, emission from relativistic electrons corkscrewing in magnetic fields. These electrons might be byproducts of dark matter particles annihilating one another, he suggested. That idea didn’t win over many converts. In a 2012 blog reflecting on the bubble saga, Finkbeiner wrote, “I was a young postdoc, claiming the haze might be a sign of dark matter annihilation, when many colleagues did not accept the haze was even there at all. This sounded like crackpot territory.” But despite taking the hint that “it would be good to work on something else for a while,” Finkbeiner eventually came back to the haze. In 2007 he partnered with Dan Hooper (Fermilab) and Gregory Dobler (then also at the CfA) to report that the WMAP haze was consistent with what would be produced by theoretical particles called WIMPs (AS&T: August/September 2013, page 32). Dark matter or not, Finkbeiner’s haze split the community. Some astronomers

From end to end, the Fermi bubbles (pink, illustrated using data from NASA’s Fermi Gamma-ray Space Telescope) span about 50,000 light-years. The purple edges are from X-ray observations by the German-led ROSAT from the 1990s. The full bubbles do not appear in X-rays, although hints of what might be their edges do. NASA GSFC

found it in their data; others — including the WMAP team — did not. The problem lay in the peeling process. Astronomers need a map of foreground sources in order to remove those sources from the data. But in many cases, observers create the smear map they use from the very same observations they’re analysing. They sort signals based on certain assumptions, and these assumptions influence what the final layers look like. They could even create a layer that isn’t really there.

Gamma-ray Giants In 2010, on their quest to prove the WMAP haze existed, Dobler, Finkbeiner, and their colleagues turned to another space observatory, NASA’s Fermi Gamma-ray Space Telescope. Fermi observes at energies up to a million billion times higher than those WMAP detects, but the team expected to see signals with both spacecraft because electrons moving fast enough to emit synchrotron radiation should also joust with nearby photons, kicking the photons up to gamma-ray energies. “It was a very dramatic thing when the data first came out,” Dobler recalls. And as soon as they made the maps, the astronomers found what they were looking for: a huge gamma-ray structure appeared right in the centre of the galaxy, right on top of the microwave haze. This haze stretched

even farther than the microwave signal, reaching 50° above and below the disk and spanning half the sky. “If your eyes were sensitive to gamma rays, you would be blown away every time you looked outside,” he says. Assuming the gamma-ray radiation indeed comes from electrons (and not everyone agrees that it does), both it and the synchrotron emission come from electrons ramped up to at least a few gigaelectron volts, corresponding to velocities 99.99999999995% the speed of light. In contrast, a typical electron in interstellar space moves at less than 1% the speed of light. But the gamma-ray signal had a weird shape. More careful analysis revealed that it had hard edges: the “fog” was in fact two humongous lobes, regions filled by tangled magnetic fields and plasma containing 1023 times www.skyandtelescope.com.au 39

Galactic Crime Scene

Astronomer Doug Finkbeiner stumbled across a faint haze of particles around the Milky Way’s centre that proved to be one of the largest structures in the galaxy. He and his colleagues spent years trying to conﬁrm the puzzling discovery.

The last decade's worth of accumulated evidence has still left a major mystery unsolved: what created the bubbles in the ﬁrst place?

MENG SU ET AL / ASTROPHYSICAL JOURNAL 2010

DOUG FINKBEINER / ASTROPHYSICAL JOURNAL 2004

ERIN CRAM

WMAP 23 GHz (microwave)

Fermi 2 GeV < E < 5 GeV (gamma ray)

Centre map: Shown here at a frequency of 23 gigahertz, the WMAP haze only appeared after its discoverer removed signals from other sources. Bottom map: Meng Su, Tracy Slatyer, and Doug Finkbeiner found that the haze was actually two gigantic bubbles. The trio won this year’s prestigious Rossi Prize in high-energy astrophysics for their discovery of the surprising Fermi bubbles.

more energy than the Sun radiates each second. Inside, the gas is about onetenth as dense as the material outside the bubbles, but a lot of high-speed particles zoom around in there, too. Although the lobes’ bases hide in the galaxy’s plane, they appear to anchor in the Milky Way’s core. A magnetic sheath encases each bubble along its edge. The edges undermined the dark matter hypothesis: edges imply an event, such as an explosion, but dark 40 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

matter annihilation would continuously generate particles and therefore create a hazier distribution. “It’s somewhat unusual to discover something in a subfield that you have nothing to do with, just because you tripped over it while looking for something else,” says Finkbeiner. “I’m in the uncomfortable position of not really being an expert at all in this kind of thing, even though my colleagues and I found it.” Further study only made the edges more problematic. The Fermi bubbles appear uniformly bright across their surfaces and at their boundaries — no limb darkening as we see on the Sun, but no edge brightening, either. That means the particles responsible for the emission are whizzing around like giddy bees not only near the bubbles’ bases but also higher up toward the top and even at the edges. Electrons would have only a few million years to make it from the galactic centre to the bubbles’ tops before losing their high energies (and normally they shouldn’t make it so far). That is a very short amount of time to blow bubbles 25,000 light-years long.

Planck Steps In Contrary to the discoverers’ hopes, the Fermi bubbles failed to sway all naysayers of the microwave haze. Although the gamma-ray features were clearly real, WMAP mission scientists continued to find no concrete evidence for the haze. That left the haze debate at the mercy of ESA’s Planck satellite. Planck launched in 2009 to follow up on WMAP’s CMB study, covering a much broader range of frequencies. Planck also improved on WMAP’s angular resolution by roughly a factor of two. Coupled with the satellite’s superb sensitivity, the heightened angular resolution gave Planck an

unprecedented view of the microwave universe, and as a result refining key cosmic parameters (AS&T: July 2013, page 14). Planck’s scientists decided to use the foreground detritus in their CMB observations to vet the mysterious microwave haze. First, they looked for it using the simple approach of peeling apart layers of data, as Finkbeiner and others had done. But then they tried a more complex, comprehensive approach. Instead of starting with prefab maps, they carefully took apart all the satellite’s data at the same time, sorting each piece into different categories — such as “dust” or “cosmic microwave background” — as they went. Then they built new maps with these sorted pieces and compared them with the regular maps in order to confirm their results. “We started this trying to actually take down the claim of WMAP conclusions from Finkbeiner and others, hoping that their analysis was, frankly, circular,” admits Krzysztof Górski (JPL and Warsaw University Observatory, Poland). But the Planck results, reported in 2012, didn’t work out that way. “What we ended up with was essentially confirming [the bubbles’ existence],” he says.

Villain on the Loose The last decade’s worth of accumulated evidence has still left a major mystery unsolved: what created the bubbles in the first place? There’s a long list of contenders, but the answers basically fall into two categories: either supernovae did it, or the galaxy’s central black hole did. Planted in star-forming clusters around the galactic centre, bursts of supernovae could blast out the particles that make up the bubbles, their explosions feeding the lobes’ bases like helium tanks inflating

Galactic plane at 23 GHz, after preliminary analysis Signal amplitude (relative to observed frequency)

0.2

-0.1 Four-component template model (to be subtracted) Signal amplitude (relative to observed frequency)

0.2

-0.1 Residual signal after template subtraction 0.10 Signal amplitude (relative to observed frequency)

balloons. Two facts favour this hypothesis. First, the galactic centre is one of the most active star-forming regions in the Milky Way, so it’s constantly producing the massive stars that go supernova. Second, astronomers know that supernova outflows create lobes, some of which can erupt out of a galaxy’s disk. A few hundred thousand stellar bombs might be able to inflate the Fermi bubbles — although it would take at least 100 million years, meaning the emission Fermi detects would only be from the latest pulse of star formation. Among the evidence offered for supernovae are recent radio observations by Ettore Carretti (CSIRO Astronomy and Space Science) and colleagues that reveal what look like ridges of polarised emission in the bubbles. Polarisation arises in the presence of orderly magnetic fields, which astronomers would expect from structures formed by supernovae. Observers had previously failed to find a strong polarisation signal, suggesting that the fields inside the bubbles were turbulent. If the ridges Carretti’s team detected are indeed related to the bubbles, they might reveal a lot about the bubbles’ origin. But there are oddities in the observations that make several researchers doubt the result. Some astronomers think the gamma-ray signal is being produced by high-speed protons instead of electrons. The supernova explanation is particularly attractive to this group, because active regions of stellar birth and death accelerate vast quantities of protons as cosmic rays. Protons might sidestep some problems with explaining the high particle velocities and the bubbles’ young age. But a black hole outburst could pump out protons, too. The second possible culprit behind the Fermi bubbles is the Milky Way’s own supermassive black

-0.05

ESA’s Planck mission picked up an assortment of microwave signals in the Milky Way (top). The Planck team created a template of known types of microwave emission (centre), which the researchers “peeled” away from the original observations. In doing so, they detected the two Fermi bubbles (bottom).

The Milky Way isn’t the only galaxy with a belching problem: dozens of galaxies have extended structures shooting from their centres. Those from Centaurus A, for example, may stretch 10 times longer than the Fermi bubbles, with strong evidence for shock waves and photons being kicked up to high energies by speedy particles. Not all these outﬂows have the same origin. Astronomers blame some on voracious supermassive black holes, which can create galaxy-scale balloons as they gobble gas. Others likely come from bursts of star birth and

NASA / CXC / CFA / ROBERT KRAFT ET AL

PLANCK COLLABORATION (3)

death in the galaxies’ cores. The two scenarios might not even be exclusive: NGC 3079, for example, has ﬁngerprints from both black hole jet and starburst activity. Although bubbles are common in galaxies with lively black holes, many of these active galaxies also have ramped-up star formation in their centres. But there may be a time delay between these two processes, potentially as much as a couple hundred million years. If astronomers can pin down the timing of these bubble structures, they might gain a better understanding of their causes.

This image from NASA’s Chandra X-ray Observatory shows the jets and bubbles emanating from the core of the galaxy Centaurus A. The jet on the left side extends 13,000 light-years.

www.skyandtelescope.com.au 41

Galactic Crime Scene

Potential Origins for the Milky Way’s Fermi Bubbles A

Stars and/or gas dumped onto black hole

Multiple star formation outbursts occur in galactic centre

Enlarges accretion disk

Wind

Jet

Heat from disk launches gas, wind off disk into space

Accretion turns on jet

Stars supernova, expel winds, accelerate particles

Expanding outflow blocked on sides by galaxy’s spiral disk

Jet blows lobes (could require multiple jets to create full-size Fermi bubbles)

Supernova outflows combine to form two lobes

Outflow funnelled into dumbbell shape by galaxy’s spiral disk

Not to scale 42 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

Astronomers disagree on the most likely origin of the Fermi bubbles. In scenarios that favour the black hole (A), material dumped onto the black hole forms a giant accretion disk. This material could either launch a wind that is then funnelled into a bubble shape by the galaxy’s disk (left) or turn on a jet that blows out surrounding material. In supernova scenarios (B), outﬂows from the vast stellar population in the galactic centre combine to form the lobes. S&T: LEAH TISCIONE

Mounting evidence suggests that the Milky Way's black hole has thrown its share of tantums in the past. hole, a behemoth “weighing” 4 million Suns that’s nestled in the galaxy’s heart. The black hole offers multiple solutions to the bubble enigma. A jet could blow out the gas and dust sitting around the galactic centre, similar to how you would blow an air bubble in a glass of water with a drinking straw. Mounting evidence suggests that the Milky Way’s black hole has thrown its share of tantrums in the past, from X-ray echoes and jetlike features to tantalising hints of an ultraviolet flash bathing the Magellanic Stream a few million years ago. But these jetlike features don’t align with the galaxy’s spin axis the way the bubbles do. Plus, it would take either a precessing jet or several jets to make the lobes as wide as they are — more than 15,000 light-years at their widest. That calls for a source that’s a little wider, perhaps an accretion disk. A feast of infalling gas would form a giant disk around the black hole. As material in the inner disk fell toward the black hole, it would heat up, radiating so strongly that it could launch a powerful wind of gas off itself. The disk’s intense radiation would continue to push on this diffuse gas, shoving it out at relativistic speeds. The gas would pick up more material as it propagated outward, eventually clearing out the bubbles. This disk-wind scenario avoids the shape problem. The outflow would naturally expand spherically in all directions, but in the galactic centre it would be pinched in on its sides by the thicker gas and dust in the galactic plane. The outflow would consequently funnel out in the directions of least resistance (along the galaxy’s rotation axis) and thereby produce the observed dumbbell shape. The scenario might also explain two rings of young stars

After careful analysis, the haze Finkbeiner discovered shows up clearly in Planck data at 30 and 44 GHz (top). The haze lines up with the Fermi bubbles as seen from 10 to 100 GeV (bottom, blue).

near the black hole, which could have formed from the outer sections of the giant accretion disk. An accretion-driven outflow, whether from jets or a disk wind, prevailed as the prime suspect at an April 2013 Fermi bubble workshop organised by Finkbeiner and others. But the larger community is still divided. Planck’s polarisation data, part of which is set to be released later this year, might bring some answers. The strength of the polarisation signal could reveal which processes accelerate the particles inside the bubbles and keep their energies high: stronger polarisation means more shocks, with the particles bouncing between the waves like a tennis ball ricocheting off two converging rackets; weaker polarisation means more turbulence, with the particles energised by

billowing magnetic fields. Astronomers are also working on the complex calculations needed to follow all the major players — including electrons, protons, and magnetic fields — that will allow them to carefully compare their theories with reality. And so even after so much toil, the case is not closed on the Fermi doublebubble. “It was completely hidden from view up until 2003, and then all of a sudden, in the span of a decade, we went from detection of this hazy, fuzzy blob toward the galactic centre to an incredibly detailed view,” Dobler says. “And yet we still have no idea exactly what it is. It’s one of the biggest structures in the galaxy, and we just don’t know. Amazing.” ✦ Assistant editor Camille M. Carlisle loves writing about anything that has to do with supermassive black holes. www.skyandtelescope.com.au 43

AS & T Test Report Dennis di Cicco

iOptron’s New ZEQ25GT Mount There’s more to this equatorial Go To mount than just a radical new design.

ZEQ25GT Price: from $1399 (including tripod and polaralignment scope) Available from local iOptron dealers. See page 97 for a list of iOptron dealers in this issue.

Tipping the scales at only 4¾ kilograms without the counterweight shaft, the ZEQ25GT is compact and very portable. The pivoting counterweight shaft clears the tripod legs when the mount is set for low latitudes all the way to the equator. ALL PHOTOS BY THE AUTHOR UNLESS OTHERWISE CREDITED

44 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

omeone can correct me if I’m wrong, but I can’t recall a company ever offering a wider variety of telescope mounts than iOptron currently does. From small and midweight alt-azimuth designs to a range of German equatorials, the company has the biggest selection of Go To mounts available today. Although iOptron’s lineup stops short of the massive “observatory” equatorials used by elite astrophotographers, its offerings fully cover the workhorse needs of amateur astronomy. I’ve spent decades using portable equipment everywhere from my driveway to the Australian Outback, and there’s never been an occasion when I wouldn’t have been well served by one of the mounts currently available from iOptron. One of the company’s newest Go To equatorials is the ZEQ25GT. It is touted as a “Z balanced” design because it has the telescope and the counterweights at opposite ends of the polar axis. Compared to a traditional German equatorial mount, the ZEQ25GT’s centre of gravity is closer to the middle of the equatorial head, leading to better inherent stability. As such, the mount’s designers could keep the ZEQ25GT’s weight low relative to its specified 12¼-kilogram telescope load capacity. Indeed, without the counterweight shaft attached, the whole equatorial head weighs only 5 kilograms. The ZEQ25GT proved to be remarkably stable for its small size and light weight, but initially I had to wonder why iOptron’s engineers

Left: Mentioned in the text, iOptron’s CEM60 (seen here at its unveiling last November at the Arizona Science & Astronomy Expo) is another equatorial mount with a “balanced” design. Below: A bubble level and latitude scale aid in setting up the ZEQ25GT quickly in the ﬁeld. Care is needed when attaching cables to their respective ports because many use identical modular jacks. S&T: SEAN WALKER

in China undertook such a radical redesign to shave what would have been only a few kilograms from a traditional German equatorial of the same load capacity. An answer to this question may have come last November with the unveiling of iOptron’s CEM60 at the Arizona Science & Astronomy Expo in Tucson. A variant of the ZEQ25GT’s design, the CEM60 also offsets the telescope from the end of the polar axis, keeping the centre of gravity near the middle of the mount. It appears that iOptron is making a concentrated effort to increase the load capacity and performance of portable equatorial mounts. It’s an admirable accomplishment that helps the majority of amateur astronomers who, like me, frequently set up and break down equipment when they observe. Take one look at the ZEQ25GT’s

profile from the side and you immediately see where the “Z” in the mount’s name comes from. But I also sense a bit of nationalistic pride in the moniker, since Mandarin-speaking Chinese call their country Zhongguo. And speaking of names, one might ponder whether this design is a significant enough departure from the traditional German equatorial mount to be called something entirely new. That’s for the astronomical community to decide, but for me the “Z” in the name serves as a nice reminder that this is a Chinese-designed equatorial mount.

Notes from the Field Despite its unusual design, the ZEQ25GT sets up and operates just the same as a conventional German equatorial, and anyone familiar with a traditional equatorial mount will

WHAT WE LIKE: ● Excellent Go To and tracking performance ● Highly portable with good load capacity for its size and weight ● Quiet operation, especially when slewing WHAT WE DON’T LIKE: ● Obstructed GPS antenna (see text) ● Limited astronomical information for objects in database

www.skyandtelescope.com.au 45

AS & T Test Report

Above left: To help with balancing the mount, the right ascension and declination drives have gear switches (arrowed) that release the worms from their worm wheels. Above right: The hand control has variable-brightness illumination for the display and buttons. The illumination automatically turns off during periods of inactivity, but returns the moment any button is pressed.

have no problems using this one. Furthermore, the heavily illustrated Quick Start Guide clearly explains the basics as well as features specific to the ZEQ25GT, such as the quick-release “gear switch” that disengages the worm gears from the worm wheels on the

The mount is available with an optional hard-sided carrying case and soft-padded tripod bag with shoulder straps.

46 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

right ascension and declinations axes. When the gears are disengaged, the axes swing freely, making it very easy for you to precisely balance the mount on both axes. The mount we borrowed from iOptron for this review came with an optional polar alignment scope. As I’ve mentioned in previous reviews of iOptron equipment, I’m very impressed with this alignment system for its simplicity and accuracy. The scope’s illuminated reticle has two sets of concentric rings graduated into 12 hours. They are for use with Sigma Octantis in the Southern Hemisphere and Polaris in the Northern. Based on the date, time, and location stored in the mount’s electronics (more about this in a moment), the hand control graphically displays where you need to position either of these stars on the reticle to achieve accurate polar alignment. There are no calculations necessary on the user’s part. For example, let’s say the hand control indicates putting Sigma Octantis at the 7h 30m mark. You just view through the polar scope and use the fine-motion screws on the mount’s azimuth and altitude adjustments to move Sigma Octantis in the field of view until it’s at the reticle’s 7h 30m mark and you’re done. If you own an Apple mobile device running iOS

6.0 or later, I highly recommend you purchase iOptron’s Polar Scope app ($1.99 from the iTunes App Store — search for “iOptron”). I find the app visually easier to use for determining the alignment star’s correct position on the reticle. The ZEQ25GT has a built-in GPS receiver for automatically setting the mount’s date, time, and geographical coordinates. But there’s a caveat. The receiver’s antenna is located in the mount’s main electronics module, which is attached to the top of the polar-axis housing. As such, it does not have a clear view of the sky when the mount is set up in its initial “home” position with the telescope above the polar axis and pointed toward the celestial pole. In this position, the declination drive blocks the antenna’s sky access, which is needed to get a fix from the GPS satellites. Indeed, I was never able to achieve a GPS fix with the mount in the home position. The simple solution is to swing the polar axis until the declination drive is far to the east or west side of the mount before powering up the electronics (an easy task thanks to the gear switch mentioned earlier). After a minute or two an audible beep and a message briefly appearing on the hand-control’s display will alert you

to the mount achieving its GPS fix (assuming there aren’t other significant sky obstructions due to trees or buildings). You can then swing the polar axis back to the home position and proceed with the initialisation of the Go To pointing using any of several alignment methods involving stars or solar system objects. Of course, you can dispense with the GPS altogether and manually input the data. Whether you or the GPS enters the data, the electronics retain the information and the correct time when the mount is powered off thanks to a user-replaceable button battery in the hand control. Thus, unless you move to a significantly different location that warrants new geographic coordinates (think tens of miles), the electronics will be immediately ready to use on subsequent nights.

The ZEQ25GT is lightweight enough to carry around with a telescope attached. The author did most of his testing with a pair of 4-inch refractors, including the Tele Vue NP101 pictured here.

I could send the scope to targets across the entire sky and always have them appear in the ﬁeld of a low-power eyepiece. Lasting Impressions The take-away feeling I got from using the ZEQ25GT for several months during the course of last year is that it’s a very good performer for its compact size and light weight. I spent most of my time using it with a pair of 4-inch (10-cm) refractors, but I also tried it with an 8-inch (20-cm) Schmidt-Cassegrain tube assembly. Although these scopes were all well within the mount’s specified weight capacity, I don’t think the mount would be a good match for apertures larger than the 8-inch, at least not with the standard tripod supplied with the mount. There is, however, an optional tripod available that has 2-inchdiameter legs, rather than the 1½-inch legs on the standard model. The ZEQ25GT made a superb platform for camera-only astrophotography. Although Comet ISON’s post-perihelion apparition was a bust (see page 32), my advanced preparations included testing the

mount with a pair of heavy DSLR bodies and a variety of lenses. The whole kit was relatively lightweight and highly portable. And even speedy setup in the field using just the polaralignment scope was more than adequate for 5- to 10-minute unguided exposures with lenses up to 180-mm focal length. Having the telescope mounted on the north end of the polar axis didn’t cause any unusual problems. As with conventional German equatorial mounts, there are parts of the sky where you have to be careful to avoid having the telescope run into the tripod legs. In general, the ZEQ25GT offered a little more “open” access to the southern part of the sky, whereas a conventional German equatorial gives the nod to the northern part. The only time I really noticed a difference between the two styles of mounts was when I observed (from the United States) around the southern meridian with the ZEQ25GT and SchmidtCassegrain, since I found myself shouldering up to the equatorial head and straddling the northern tripod legs. The Go To pointing of the ZEQ25GT was well above average. Most nights I’d use a “one-star alignment” to initialise the pointing after adjusting the mount on the celestial pole with only the polaralignment scope. With the telescope

set in the home position, selecting the one-star alignment automatically sends the scope to the approximate location of a bright star you pick from a list displayed on the hand control. You use the control’s push buttons to move the scope until the star is centred in the field of view, press the “enter” key, and your Go To slewing is ready to use. I could send the scope to targets across the entire sky and always have them appear in the field of a lowpower eyepiece. There was one other aspect of the ZEQ25GT that I really liked — the way it sounds when slewing. I find the typical howling motors of most Go To scopes really annoying. But the new iOptron drive was not only far quieter than most Go To scopes, its sound was much more pleasant. It didn’t intrude on the serenity of the night sky nearly as much as most other Go To mounts do. Overall the ZEQ25GT proved to be a very capable equatorial mount. It was an ideal companion for the 4-inch refractors, since I could leave these scopes on the mount and carry the whole setup into the yard in one trip. Polar alignment is fast and the Go To pointing accurate, making spur-ofthe-moment observing a breeze Ø Senior editor Dennis di Cicco has been guiding telescopes for deep-sky photography since the 1960s. www.skyandtelescope.com.au 47

New Product Showcase

Î APP SCOPE Celestron introduced its new COSMOS Series of binoculars, microscopes, and telescopes at the 2014 Consumer Electronics Show in Las Vegas. Of particular note is the COSMOS 90GT WiFi Telescope (pictured at left), a Go To refractor completely controlled using the free COSMOS Celestron Navigator app for iOS and Android devices. This 90-mm (3.5-inch) f/10 achromatic refractor is mounted on a single-arm alt-azimuth mount with a sturdy aluminium tripod. Simply set the telescope down, open the COSMOS Celestron Navigator mobile app, and the “3D Spaceship of the Imagination” design on the fork arm lights up when your device successfully connects to the mount. Follow the alignment procedure of your choice, and you’re ready to observe using a controller you’re most familiar with — your own smartphone or tablet device. The COSMOS Celestron Navigator mobile app contains a complete planetarium program, enabling you to seek out the Moon, planets, and many of the brighter deep-sky objects visible from your location. The COSMOS 90GT WiFi Telescope comes with a StarPointer red-dot finder, 25- and 10-mm Kellner eyepieces, and a rubberised accessory tray with an angled smartphone platform. If you don’t have an iOS or Android mobile device, an optional hand controller is available from the manufacturer. See the company’s website (www.celestron.com) for additional details. Celestron Available from local Celestron dealers. See page 97 for a list of dealers in this issue.

Î COMPACT ASTROGRAPH Takahashi has updated and reintroduced its smallest Epsilon series telescope, the ε-130D Hyperbolic Astrograph ($3,205). This 5-inch (13cm) f/3.3 optical system features a hyperbolic primary mirror mated with a digital corrector to record pinpoint stars across a large 44-mm image circle. With a newly redesigned collimation system, secondary assembly, and heavy-duty focuser, the ε-130D will hold alignment at any angle as you track your targets across the sky. Its compact Newtonian design measures around 46 centimetres and weighs in at 4.9 kilograms, making the ε-130D airline transportable. The reduced size and weight also allow it to be used on smaller equatorial mounts than its predecessor could. See the company’s website for additional options. Takahashi Available in Australia from Astronomy & Electronics Centre www.astronomy-electronics-centre.com.au

New Product Showcase is a reader service featuring innovative equipment and software of interest to amateur astronomers. The descriptions are based largely on information supplied by the manufacturers or distributors. Australian Sky & Telescope assumes no responsibility for the accuracy of vendors’ statements. For further information, contact the manufacturer or distributor. Announcements should be sent to contributions@skyandtelescope.com.au. Not all announcements can be listed.

48 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

OBSERVING MAY/JUNE 2014

IN THIS SECTION 50 Binocular Highlight: Near and Far in Coma Berenices

64 Exploring the Moon: History of the Moon

51 Southern Hemisphere Sky

66 Exploring the Solar System: When Seeing Isn’t Believing

52 Tonight’s Sky: Splendid Spica 68 Double Star Notes: In the Coils of the Sea Serpent 54 Sun, Moon & Planets: Saturn Shines All Night

70 Targets: The Realm of the Nebulae

56 Planetary Almanac

74 Going Deep: Digging Deep in Messier 83

60 Celestial Calendar 60 Saturn Double Header 61 Prospects for a Near-Earth Comet 63 AH Scorpii

Saturn is at opposition in May and visible all night. Here’s how Saturn would look to the human eye if you were sitting in a spacecraft above the ringed planet, a view not obtainable from Earth! This image was taken last October by NASA’s Cassini spacecraft, in orbit around Saturn since 2004. NASA ⁄JPL-CALTECH ⁄ SSI ⁄CORNELL

www.skyandtelescope.com.au 49

Gary Seronik Binocular Highlight

USING THE STAR CHART WHEN

HOW

M17

SCUTUM M25

M22

NOTE: The map is plotted for 35° south latitude (for example, Sydney, Buenos Aires, Cape Town). If you’re far north of there, stars in the northern part of the sky will be higher and stars in the south lower. Far south of 35° the reverse is true.

Fa ci

50 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

M11

you’ll find a nice, wide double: 17 Comae Berenices. Its components shine at magnitude 5.3 and 6.6 and are separated by a generous 145" — an easy split for any binoculars. If Mel 111 plays to binocular strengths, then NGC 4565 exposes their greatest weakness. This galaxy is situated just off the cluster’s eastern edge. While relatively large for such an object, it appears tiny at the low magnification typical for binoculars. To make matters worse, the galaxy is also quite faint. Although it’s listed at magnitude 9.5, NGC 4565’s surface brightness is low. Indeed, 10×50 binoculars don’t show it well even under dark skies. That’s not surprising when you consider that NGC 4565 lies approximately 40 million light-years beyond the stars that make up Mel 111. It’s truly a background object. ✦

map so the label “Facing SW” is right-side up. About a third of the way from there to the map’s centre is the brilliant star Canopus. Go out and look southwest nearly a third of the way from horizontal to straight up. There’s Canopus!

S E R P E ( C AU DN S A)

ike any tool, binoculars have their strengths and weaknesses. They excel at showing big swaths of sky but don’t do as well with objects that are small and faint. One constellation that features both extremes is Coma Berenices. Coma’s binocular prize is the vast open cluster Melotte 111, often called the Coma Star Cluster. It’s exactly the kind of object that binoculars show better than telescopes. It’s so large that it seems to spill out of the field of view even in ordinary binoculars. One reason is because it’s less than 300 light-years away, making it one of the nearest star clusters to our solar system. The grouping sparkles with the light from some two dozen stars brighter than magnitude 8. As an added bonus, on the eastern edge of the main clump of cluster stars,

FOR EXAMPLE: Turn the

Fa c i n g E a st

Near and Far in Coma Berenices

COMA BERENICES

Go outside within an hour or so of a time listed above. Hold the map out in front of you and turn it around so the label for the direction you’re facing (such as west or northeast) is right-side up. The curved edge represents the horizon, and the stars above it on the map now match the stars in front of you in the sky. The centre of the map is the zenith, the point in the sky directly overhead.

ar vie w

cul

M64

These are standard times.

5°

4565

11pm 10pm 9pm 8pm 7pm

Mel 111

Late April Early May Late May Early June Late June

ONLINE You can get a sky chart customised for your location at any time at SkyandTelescope.com/ skychart

–1 0 1 2 3 Star 4 magnitudes

Fa c i n g N o r t h 13h 10h

Fa ER NC

M3 δ

M44

S ENT) RPPU S EC A (

VIRG

M67

0°

CANIS MINOR

S h

Procyon

F a c i n g We s t

MONOCE

ROS

M93

CA MA NIS JOR

BA M LU

M41

η ε

PU no

c Fa

Galaxy Double star Variable star Open cluster

1h –60°

ANA

NA s pu

Small Magellanic Cloud

TUC

UM CUL

RETI

I AR

47 Tuc

C PI

ge Lar llanic ge d a M lou C

HYDRUS

–80° β

30 D

C α

O C TA N S

CHAMAELEON VOL VO

M47

M46 ρ λ

–80°

ANS

PYXIS

A L E δ ι

MUSCA β

A S N I O L R A O R C ST U A

US α β TRI γ AN AU GU STR LUM ALE α APUS

CIN

ar ηC

Hadar β

N ζ

PIUS

–60°

γ η

RUS CRUX γ

Antares

TAU

M48

Alph

ANTLIA

SCOR

Rigil Kent

ard

–20°

δ σ τ

M62

CEN

A D R H Y

AN T EX ν

E AT CR

Spica

A β

M19

M20

CIR

639

LIBR

ζ η ξ

SC OP

COR V

M12 M10

ω Cen

I τ

Zenith

–40°

E Q U A T O R

Sirius

OPH

A N IS RO AL CO RE α BO

urus Arct

+20°

LE O

16h

COMA BERENICES

ÖT

kl e

M L I NE 0 OR Si

+40°

M51

CANES V E N AT I C I

U M AR S A JO R

T I C L I P E C

Achernar

O HOR

LOG

IUM

Diﬀuse nebula Globular cluster Planetary nebula

Fa c i n g S o u t h www.skyandtelescope.com.au 51

Fred Schaaf Tonight's Sky

Splendid Spica There’s more than meets the eye to Virgo’s sole bright star.

ne of my most cherished astronomical memories was formed on the night of April 12–13, 1968. I was 13 years old, and I had received my first really useful telescope a few months earlier. I had already seen a few total lunar eclipses, but that night was when I first viewed one through a telescope. And not just any total eclipse of the Moon — though all of them have their attractions. During this event, as the Moon dimmed and reddened, a 1stmagnitude star flamed into vastly greater splendour incredibly close to the Moon. That star was Spica, and it has been one of my favourites ever since. Most of you are probably first reading these words in April and may have been favourably placed to catch total lunar eclipse of April 15. The Moon was fairly close to Mars and quite close to Spica during this eclipse, though its separation from the star was much greater than when I witnessed it all those years ago. Regardless of whether clouds let us see this eclipse, I want to share some facts and observations relating to spectacular Spica. The ear of wheat. Many amateur astronomers know that the name Spica is Latin for “ear of wheat,” a translation of the Greek name Stachys. That’s because the star marks the ear (or spike) of wheat being held by Virgo when commonly imagined as Ceres, the ancient Roman goddess of agriculture and living things. The word “cereal” is derived from her name, and of course the goddess also gives her name to the largest asteroid, the socalled dwarf planet Ceres. It’s interesting that the asteroids Ceres and Vesta are putting on a great show this autumn and early summer right here in Virgo, just 15° north or northeast of Spica (see last month’s issue, page 60, for a finder chart). Spica’s suns. Five of the sky’s 20 brightest stars have spectral types between B0 and B3 — hotter than Rigel or Regulus. All of them are

Virgo is shown mirror-reversed in this 1687 chart, with the star Spica atop a sheaf of wheat. North is to the right. JOHANNES HEVELIUS

52 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

visible from southern latitudes. Actually, Spica consists of at least two extremely luminous blue stars, roughly seven and four times wider than the Sun. The brighter, larger Spica component has a mass about 11 times the Sun’s, and so it should someday go supernova. Spica’s stars have an average separation of only 18 million kilometres, and they orbit each other in just over 4 days — during which the changing orientation of their ellipsoidal shapes cause the point of light we see as Spica to vary slightly in brightness. The larger component also pulsates, adding up to a net variation between magnitude 0.92 and 1.04.

Sun and Spica simultaneously. In years long after the 1968 lunar eclipse, I’ve twice seen the Moon occult Spica. The most memorable observation featured Spica emerging from behind the Moon just after sunrise. I was able to keep seeing Spica in an 8×50 finderscope for quite some time as the Sun grew higher. Spica’s spark was visible in one eye while, at the same time, my other (unaided) eye beheld the Sun peeking through trees: two stars seen together in the daytime sky. ✦ Fred Schaaf welcomes your comments at fschaaf@aol.com.

www.opticscentral.com.au

Address: 8/23 Cook Rd, Mitcham VIC 3132. Ph: 1300 884 763, Email: support@opticscentral.com.au

Sun, Moon and Planets Greg Bryant

Saturn Shines All Night May sees the ringed planet reach opposition.

ars and Jupiter will entice observers as soon as the sky darkens, and then Saturn will be

on show. Mercury reappears in the western evening twilight sky in May after passing through solar conjunction in April. It’s not a good apparition, though, for Southern Hemisphere observers as Mercury will remain low. By the time Mercury becomes visible, it will be in the constellation Taurus where it remains until just before the end of May. At its best, around the time Mercury reaches greatest elongation east (23o) of the Sun on the 25th, it’s setting around the time the sky has fully darkened. Late May sees Mercury move into Gemini, and a few days later, on 2 June, Mercury will pass in front of M35, although the spectacle will be diminished by the twilight sky and low altitude. From here on, Mercury sinks back quickly towards the Sun, lost from view by midJune. The planet is in inferior conjunction with the Sun on 20 June and reappears in the dawn sky by month’s end, back in Taurus. May and June is the last chance to observe Jupiter before it passes through conjunction with the Sun in July. The King of the Planets begins May at magnitude -2.0, fading to magnitude -1.8 by the end of June. With an average size of about 33” in diameter during this period, Jupiter displays a much smaller disk compared to the 47” at opposition back in January. Located near Gemini’s Twins, Castor and Pollux, Jupiter slowly makes its way towards the 4th magnitude double star Delta (δ) Geminorum, passing within 0.5o of the star on the 23rd. Look for the Moon near Jupiter on the nights of 4 May, 1 June, and 29 June. Mars is now past opposition but it still commands attention in the northern sky. During these two months, Mars will shrink in size from 14.5” to 9.5”, and drop in brightness from magnitude -1.2 to 0. The apparent motion of Mars slows as it reaches its stationary point on 21 May and then begins to move towards Spica, with the two being about 6o apart by the end of June. The Moon will be near Mars on 11 May and 8 June.

Sky positions In Sun, Moon, and Planets, most descriptions that relate to your horizon or zenith — including directions like up, down, right, and left — are written for skywatchers in the world’s mid-southern latitudes. Conﬁgurations of the Moon with speciﬁc planets are a special case because they also depend on longitude, and these are given for Australia.

54 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

December solstice

March equinox

Mercury

Sun

Sept. equinox

Venus

ORBITS OF THE PLANETS The curved arrows show each planet’s movement during May and June. The outer planets don’t change position enough in a month to notice at this scale.

Mars Earth June solstice

Jupiter Uranus Saturn Neptune Pluto

Saturn is at opposition on 11 May and will be well-placed throughout May and June, visible all night and at its best for this year. It’s a showpiece sight, and a wonder for newcomers to astronomy. Saturn’s rings will be tilted about 21o to our line of sight during May and June, making for an enjoyable view. If you can, for several nights around 11 May, look for the Seeliger effect, a noticeable brightening of Saturn’s rings with respect to the planet itself. Saturn also has the bonus of a retinue of moons visible in amateur scopes. See page 56 for more information. As a bonus, our Moon will occult Saturn on the night of 14 May (see page 60) and will be near the planet again on 10 June. Pluto is in Sagittarius, south of the open cluster NGC 6716. With opposition approaching in early July, this 14th magnitude dwarf planet is rising early in the evening during May and June. Neptune is rising around the middle of the night during May and June. Glowing at 8th magnitude and displaying a disk 2.3” wide, Neptune lies in Aquarius, northeast of 4.8-magnitude Sigma (V) Aquarii. On 10 June, Neptune reaches its apparent stationary point in its movement amongst the stars and will begin moving retrograde (southwest) until November. Venus is rising around 3 hours

before the Sun does during May and June. Shining brilliantly at magnitude -4, the Morning Star is in Pisces for all of May, moving into Aries at the beginning of June and then Taurus mid-June. As May progresses, Venus will close in on 5.9-magnitude Uranus, with the two being just 1.2o apart on the morning of the 16th. The Moon will be near Venus on the mornings of 26 May and 25 June, the latter date seeing the Moon midway between Venus and 1st magnitude Aldebaran. The Winter Solstice is on 21 June, at which time the Sun is at its northernmost point in our sky and daylight hours are at their shortest.

From here until December, the days will lengthen and the nights will shorten. The Moon will be 2o north of Aldebaran on 1 May and 25 June, 5o south of Regulus on 8 May and 5 June, and 2o north of Spica on 12 May and 9 June. The Eta Aquarids, one of the best meteor showers visible from the Southern Hemisphere, are predicted to peak on the morning of May 6. The Moon is at First Quarter on the 7th, so the skies will be Moon-free this year for meteor observing. Under dark skies, expect to see nearly one meteor per minute. The shower is active from April 19 – May 28, with a period from May 3 – 10 when 30 or more per hour may be seen under ideal conditions. ✦

Events Of Note May

2 4 6 7 8 11 12 14 15 21 23 25 26 29 31

Jupiter 0.3o north of 44 Geminorum Aldebaran 2o south of the Moon Jupiter 5o north of the Moon Eta Aquarids meteor shower peaks First Quarter Moon (1:15pm) Regulus 5o north of the Moon Saturn at opposition Mars 3o north of the Moon Spica 1.7o south of the Moon Saturn 0.6o north of the Moon Full Moon Uranus 1.3o north of Venus Last Quarter Moon (10:59pm) Jupiter 0.5o north of Delta Geminorum Uranus 1.9o south of the Moon Mercury greatest elongation east (23o) Venus 2o south of the Moon New Moon Mercury 6o north of the Moon

Jun

1 2 5 6 8 9 11 13 20 21

24 25 27 29 30

Jupiter 6o north of the Moon Mercury 0.2o south of M35 Regulus 5o north of the Moon First Quarter Moon (6:39am) Mars 1.6o north of the Moon Spica 1.8o south of the Moon Saturn 0.6o north of the Moon Full Moon (2:11pm) Last Quarter Moon (4:39am) Uranus 1.7o south of the Moon Solstice Pollux 6o north of Jupiter Venus 1.3o north of the Moon Aldebaran 2o south of the Moon New Moon (6:08pm) Jupiter 5o north of the Moon Venus 4o north of the Hyades

Times are listed in Eastern Australia Standard Time

www.skyandtelescope.com.au 55

Sun, Moon and Planets

Jupiter’s Red Spot Transit, May – June 2014

Satellites of Saturn

(Universal Time) MAY 1: 2:

3: 4: 5:

6: 7:

8: 9: 10:

11: 12:

13: 14:

15: 16: 17:

18: 19:

20: 21:

7:48 17:44 3:39 13:35 23:31 9:27 19:23 5:19 15:14 1:10 11:06 21:02 6:58 16:54 2:49 12:45 22:41 8:37 18:33 4:29 14:25 0:20 10:16 20:12 6:08 16:04 2:00 11:55 21:51 7:47 17:43 3:39 13:35 23:30 9:26 19:22 5:18 15:14 1:10 11:05 21:01 6:57 16:53 2:49 12:45 22:41 8:36 18:32 4:28

22:

23: 24:

25: 26:

27: 28: 29:

30: 31:

14:24 0:20 10:16 20:11 6:07 16:03 1:59 11:55 21:51 7:46 17:42 3:38 13:34 23:30 9:26 19:22 5:17 15:13 1:09 11:05 21:01 6:57 16:52 2:48 12:44 22:40

11: 12:

13: 14: 15:

16: 17:

18: 19:

20: 21:

JUNE 1: 2: 3:

4: 5:

6: 7:

8: 9: 10:

8:39 18:35 4:31 14:27 0:23 10:18 20:14 6:10 16:06 2:02 11:58 21:53 7:49 17:45 3:41 13:37 23:33 9:29 19:24 5:20 15:16 1:12 11:08

22:

23: 24:

25: 26: 27:

28: 29:

30:

21:04 7:00 16:55 2:51 12:47 22:43 8:39 18:34 4:31 14:26 0:22 10:18 20:14 6:10 16:05 2:01 11:57 21:53 7:49 17:45 3:41 13:36 23:32 9:28 19:24 5:20 15:16 1:12 11:07 21:03 6:59 16:55 2:51 12:47 22:42 8:38 18:34 4:30 14:26 0:22 10:18 20:13 6:09 16:05 2:01 11:57 21:52 7:48 17:44

These predictions assume the Red Spot is at Jovian System II longitude 210°. If it has moved elsewhere, it will transit 1.7 minutes late for every 1° of longitude greater than 210°, or 1.7 minutes early for every 1° less than 210°. Check SkyandTelescope.com/redspot for updates.

56 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

It’s Saturn time! With the ringed planet at opposition, telescopes can be turned to Saturn throughout the night during May and June, and you can seek out its brightest moons. 8th magnitude orange Titan is the easiest to spot, and a small telescope will readily reveal it. Titan spends most of its time far away from the glare of Saturn. With a diameter of 5,150 km (the largest satellite of Saturn), Titan orbits Saturn every 15.9 days, and during May/June, it will be at its greatest elongation east on 6 May, 21 May, 6 June, and 22 June. The next easiest to see is 10th magnitude Rhea, Saturn’s second largest satellite with a diameter of 1,530 km. It revolves around Saturn every 4.5 days. Dione, at 10th magnitude, resides inside Rhea’s orbit. The fourth largest of Saturn’s satellites, it completes one orbit in just 2.7 days. Also at 10th magnitude is Tethys, Saturn’s fifth largest moon. It lies closer to Saturn than Dione does, and it’s slightly smaller. Yet, it’s also just a touch brighter than Dione, due to a higher icy albedo. Enceladus at 12th magnitude is very challenging. The sixth largest Saturnian satellite, it whips around the planet in just 1.4 days, so it’s very close to the glare of Saturn. 13th magnitude Mimas is even closer to Saturn, orbiting in less than 23 hours. Iapetus orbits well beyond the above six satellites, taking 80 days to revolve around Saturn, but it’s an enigmatic satellite worth mentioning. With a diameter of 1,500 km, it’s Saturn’s third largest moon. One side of Iapetus is dark coloured and the other is light. As such, it varies from 10th magnitude (when west of Saturn) to 12th magnitude (when east of it). Key dates for Iapetus during May/June are: > 7 May: Superior conjunction > 26 May: Greatest elongation east > 14 June: Inferior conjunction

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Sun, Moon and Planets

Sun and Planets, May 2014

Satellites of Jupiter Jupiter is in the northwestern evening sky, setting early in the evening as it approaches conjunction with the Sun in July. Be sure to seek out Jupiter early and follow the motions of its four Galilean Moons The innermost of the four, Io, zips around Jupiter in 1.77 days, closely followed by Europa in 3.55 days. Ganymede takes 7.15 days, basically a week, and Callisto is almost leisurely with an orbital period of 16.69 days. These moons are quite bright, ranging between 5th and 6th magnitude, and are easily seen in small telescopes. Room doesn’t permit us here to display the changing pattern they present, but it’s worth seeking out Jupiter each night to see how they’re moving. Can you identify which moon is which?

Sun

Mercury

Venus

May

Right Ascension

Declination

Elongation

Magnitudes

Diameter

Illumination

Distance

2h 31.8m

+14° 56'

—

–26.8

31' 45"

—

1.007

4h 30.4m

+21° 50'

—

–26.8

31' 33"

—

1.014

+17° 06'

6° Ev

–1.8

5.2"

97%

1.294

4 15.9

+23° 17'

16° Ev

–0.9

5.9"

75%

1.132

5h 23.0m

+25° 30'

22° Ev

0.0

7.3"

47%

0.916

Saturn

6 03.6

+24° 40'

22° Ev

+1.1

9.3"

25%

0.724

23h 52.7m

–2° 10'

43° Mo

–4.1

17.0"

67%

0.982

+1° 58'

41° Mo

–4.1

15.8"

70%

1.056

0 35.2

1 18.3

+6° 11'

39° Mo

–4.0

14.8"

74%

1.128

2h 02.3m

+10° 18'

37° Mo

–4.0

13.9"

77%

1.197

12 43.7

–2° 57'

151° Ev

–1.2

14.5"

98%

0.644

12h 34.3m

–2° 40'

134° Ev

–0.8

13.3"

94%

0.705

91%

0.788

–3° 26'

120° Ev

–0.5

11.9"

7 04.3

+22° 55'

64° Ev

–2.0

35.3"

99%

5.592

7h 26.7m

+22° 17'

41° Ev

–1.9

33.0"

100%

5.974

+0.1

18.6"

100%

8.914

31 Jupiter

Mars

2 53.8

12 35.7 h

–15° 29' 170° Mo

15 15.1

15 06.3

–14° 56'

159° Ev

+0.2

18.5"

100%

8.960

Uranus

0h 54.8m

+5° 09'

40° Mo

+5.9

3.4"

100%

20.785

Neptune

22h 36.8m

–9° 31'

78° Mo

+7.9

2.3"

100%

30.175

Pluto

18h 56.0m

–20° 09' 132° Mo

+14.1

0.1"

100%

31.971

June

Right Ascension

Declination

Elongation

Magnitudes

Diameter

Illumination

Distance

4h 34.5m

+21° 59'

—

–26.8

31' 33"

—

1.014

6h 34.6m

+23° 12'

—

–26.8

31' 28"

—

1.017

Sun and Planets, June 2014 Sun

NÍN ANTO

K RÜ

Mercury

+24° 28'

21° Ev

+1.2

9.5"

23%

0.708

6 10.9

+21° 56'

13° Ev

+3.4

11.5"

0.585

5h 50.6m

+19° 26'

4° Mo

—

12.1"

0.557

5 35.9

+18° 43'

14° Mo

+2.7

10.7"

0.625

2h 06.8m

+10° 41'

37° Mo

–4.0

13.9"

77%

1.204

2h 52.4m

6 05.9

Moon, May 2014

Moon, June 2014

Phases

First Quarter Full Moon Last Quarter New Moon

May 7, 3:15 UT May 14, 19:16 UT May 21, 12:59 UT May 28, 18:40 UT

First Quarter Full Moon Last Quarter New Moon

Venus June 5, 20:39 UT June 13, 4:11 UT June 19, 18:39 UT June 27, 8:08 UT

Distances

Apogee 404,318 km Perigee 367,102 km

Apogee 404,954 km Perigee 362,065 km

May 6, 10h UT diam. 29' 24" May 18, 12h UT diam. 33' 09"

June 3, 4h UT diam. 29' 28" June 15, 3h UT diam. 32' 40"

Librations

May 4 May 13 May 19 May 25 May 31

June 5 June 10 June 23

Max. libration (NE limb) Min. libration (SW limb) Max. libration (SE limb) Min. libration (SE limb) Max. libration (NE limb)

Min. libration (NW limb) Max. libration (SW limb) Min. libration (NE limb)

The table at right gives each object’s right ascension and declination (equinox of date) at 0h Universal Time on selected dates, and its elongation from the Sun in the morning (Mo) or evening (Ev) sky. Next are the visual magnitude and equatorial diameter. (Saturn’s ring extent is 2.27 times its equatorial diameter.) Last are the percentage of a planet’s disk illuminated by the Sun and the distance from Earth in astronomical units. (Based on the mean Earth–Sun distance, 1 au equals 149,597,870 kilometres. For other dates, see SkyandTelescope.com/almanac.

58 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

Mars

+14° 29'

35° Mo

–3.9

13.1"

80%

1.270

3 39.7

+17° 46'

33° Mo

–3.9

12.5"

83%

1.333

4h 23.9m

+20° 08'

30° Mo

–3.9

12.0"

85%

1.386

12 36.2

–3° 31'

119° Ev

–0.5

11.8"

91%

0.794

12h 47.6m

–5° 14'

108° Ev

–0.2

10.5"

89%

0.889

Saturn

Uranus

–7° 24'

100° Ev

0.0

9.5"

88%

0.982

7 27.5

+22° 15'

40° Ev

–1.9

32.9"

100%

5.985

7h 53.1m

+21° 16'

18° Ev

–1.8

31.7"

100%

6.214

30 Jupiter

13 04.8 h

15 06.1

–14° 55' 158° Ev

+0.2

18.5"

100%

8.966

15h 00.0m

–14° 35'

129° Ev

+0.4

18.0"

100%

9.250

+5° 36'

69° Mo

+5.9

3.5"

100%

20.367

0 59.2 h

Neptune

22 37.4

–9° 28'

107° Mo

+7.9

2.3"

100%

29.658

Pluto

18h 53.4m

–20° 14' 162° Mo

+14.1

0.1"

100%

31.703

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Celestial Calendar

Saturn Double Header

Steve Kerr

ack in February, much of Australia and New Zealand had its first chance in a while to see an occultation of Saturn by the Moon. The catch was that for most locations, it was broad daylight. While the Moon is easy enough to find during the day, spotting the location where Saturn will reappear in a blue sky is not. The evening of May 14 is the next opportunity for our part of the world to view this series of occultations of Saturn. This time it will be fully dark for all locations but there is another challenge to this being an easy occultation. The Moon will be only around seven hours short of Full at the time of the encounter which means that the Moon will be very bright and that both the disappearance and reappearance will be along bright edges of the lunar disk. But isn’t Saturn a bright object? Occultations like this are an excellent demonstration of the meaning of surface brightness. Viewed separately, both Saturn and the Moon are bright objects. But the facts are that the Moon is actually a very dark object reflecting on average only 12% of the light falling on its surface. The Moon’s apparent brightness is a product of its closeness to the Sun and to us. Saturn on the other hand reflects on average around 47% of the light reaching it, but with Saturn being so much more distant from the Sun and us, the outcome is a much lower surface brightness. This becomes really obvious during an occultation like this where Saturn will appear surprisingly faint as it comes up to the bright edge. This occultation is visible across Australia south of a line running from Joseph Bonaparte Gulf in far northern Western Australia through Emerald and Gympie in Queensland. North of this line, Saturn will appear to slip past the northern edge of the lunar disk while at the edge of the zone, a strip around 35 kilometres wide will witness Saturn partially hidden. Perth observers will see Saturn disappear with the Moon only 13o above the eastern horizon while observers farther east will see it higher in the sky. Across the Tasman, all of New Zealand will see

Location

Saturn – 14 May 2014 Disappearance

Reappearance

Adelaide (ACST)

20:10

21:17

Alice Springs (ACST)

19:57

20:47

Auckland (NZST)

23:53

00:40*

Brisbane (AEST)

21:05

21:35

Canberra (AEST)

20:53

22:00

Christchurch (NZST)

23:40

00:52*

Dunedin (NZST)

23:36

00:51*

Hobart (AEST)

20:59

22:12

Melbourne (AEST)

20:50

22:00

Perth (AWST)

18:26

19:24

Sydney (AEST)

20:55

21:59

Wellington (NZST)

23:46

00:52*

*LOCAL DATE 15 MAY NZST – NEW ZEALAND STANDARD TIME – UT+12 HOURS AEST – AUSTRALIAN EASTERN STANDARD TIME – UT+10 HOURS ACST – AUSTRALIAN CENTRAL STANDARD TIME – UT+9.5 HOURS AWST – AUSTRALIAN WESTERN STANDARD TIME – UT + 8 HOURS

60 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

the occultation with the Moon high in the sky and the reappearances occurring after local midnight. Photographing these encounters is very difficult due to this contrast. A commonly used strategy is to maximise the magnification to spread out the glare from the Moon. A more effective strategy would be to combine two different length exposures, however speed will be of the essence — the Moon moves surprisingly quickly and the two images will have be captured immediately after each other to avoid blurring. The diagram above (created using David Herald's Occult software) shows the apparent path of Saturn behind the lunar disk while the table shows various times of disappearance and reappearance. Observers in other locations can interpolate both times and locations. Observers in far southwestern Western Australia will get another chance just before dawn on the 11th of June. If you are south of Bunbury and west of Esperance, the northern edge of the waxing gibbous Moon will occult Saturn just at moonset around 4:13am local time. But observers will need a perfect southwestern horizon and spotlessly clean atmosphere to be able to watch this one.✦ Steve Kerr is a Queensland-based amateur astronomer and active occultation observer.

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Prospects for a Near-Earth Comet David Seargent

ay and June will see the unusual sight of an “Earthgrazing” comet; only a faint one, but an interesting phenomenon just the same! Nevertheless, before looking at the observing prospects for this object, let’s first say a few words about two other comets. The first of these, comet C/2012 X1 (LINEAR), continues to gain altitude in the latter part of the night. Clipping Capricornus in early May, the comet then re-enters Aquarius, drifting slowly though the more southerly reaches of this constellation from the middle of the month until mid June when it passes into Piscis Austrinus. At the close of June, it will be close to the prominent 1st magnitude star Fomalhaut.

The brightness of this comet has been somewhat erratic, but on present indications it may remain close to magnitude 9 or thereabouts throughout most of this period, although a more rapid fading may happen during the latter part of June if the receding comet “switches off ” activity at similar heliocentric distances to its rather dramatic “switching on” last year. Perihelion passage occurred on February 21 at a distance of just under 1.6 au from the Sun, so it is likely that the comet will be starting to wind down activity during the period covered here. By contrast, comet C/2012 K1 (PANSTARRS) does not arrive at perihelion (1.05 au) until August 27 and as such is slowly brightening as it draws nearer the Sun. Still deep in the northern sky, the comet should

nevertheless be visible from midsouthern latitudes during May and June as it tracks a little south of west from near Eta (η) Ursa Majoris at the start of May, across Canes Venatici and into Ursa Major by the middle of the month, reaching Leo Minor at the end of the first week of June, and into Leo during that month’s final ten days. If the present slow but steady rate of brightening continues, it should be around magnitude 9 – 9.5 in early May, brightening only slightly to perhaps magnitude 8.5 – 9.0 by June’s end. Although this comet does not favour southern observers during this period, a careful watch on its behaviour will be interesting as several astronomers have pointed out a similarity between its very slow rate of brightening during 2013 and that of the ill-fated comet C/2012 S1 (ISON). Although PANSTARRS is intrinsically brighter and has a perihelion distance some one hundred times larger than ISON, there is still a chance (albeit a small one, most experts believe) that this comet will go the way of ISON and fall to pieces. If this does happen, it will be more likely around the time of perihelion in late August but hints as to its fate www.skyandtelescope.com.au 61

Celestial Calendar

may just possibly be detectable as early as May or June in the form of erratic brightness behaviour or distorted appearances of the coma. Now to the Earthgrazer! This is the intrinsically very faint comet 209P/ LINEAR, discovered on February 4, 2004 as a faint 18th magnitude speck and subsequently recovered during its next return in 2009. This year, its third perihelion since discovery, takes place on May 6 (0.97 au from the Sun). As the comet recedes from perihelion, it will pass just 0.055 au from Earth on May 29. Prior to this however, the Earth will pass even closer to the comet’s orbit and hope is quite high that a good meteor shower, with rates possibly as high as (or even higher than!) 100 – 400 per hour, will occur on May 23/24. Alas for us down under, the predicted radiant lies in the far-northern constellation of Camelopardalis, a mere 11o south of the north celestial pole. Canada and the United States will be well placed, and there is even a slight possibility of storm rates (i.e. zenith hourly rates of 1,000 or higher) being seen from those locations. The comet itself will, needless to say, also approach from the north. On May 22, it will be near the boundary of Ursa Major and Leo Minor when astronomical twilight ends in eastern Australia. During succeeding days it will swoop down through Leo, clipping Sextans and Crater, before crossing Hydra at month’s end. Continuing its rapid southward motion, the comet arrives at the edge of the Southern Cross on June 5, slowing down as it draws away from our planet and being found in Musca by the time of Full Moon on June 13. So rapid will this object’s motion be during late May and early June that “standard” ephemerides will be of little use and its position will need to be computed for suitable local times. Normally, such a close approach should mean a bright comet. However on this occasion the comet is one of very low activity and actually rates amongst the faintest known. Predictions based on its two former observed returns indicate a brightness of around magnitude 11 on May 22, possibly reaching magnitude 10 – 10.5 at closest approach before declining to about 13th magnitude in the middle of June.

Comet C/2012 K1 (PANSTARRS) Date (12hr UT)

R.A. hh mm

Dec. o ’

Delta AU

r AU

Apr 19 Apr 26 May 3 May 10 May 17 May 24 May 31 Jun 7 Jun 14 Jun 21 Jun 28

14 49.3 14 08.4 13 21.8 12 34.5 11 51.7 11 16.3 10 48.6 10 27.6 10 11.6 9 59.4 9 49.9

+44 49 +47 48 +49 24 +49 24 +47 57 +45 30 +42 33 +39 25 +36 19 +33 20 +30 31

1.541 1.491 1.472 1.483 1.520 1.577 1.648 1.727 1.808 1.888 1.961

2.245 2.162 2.079 1.996 1.914 1.831 1.750 1.669 1.590 1.513 1.438

Date (12hr UT)

R.A. hh mm

Dec. o ’

Delta AU

r AU

Apr 19 Apr 26 May 3 May 10 May 17 May 24 May 31 Jun 7 Jun 14 Jun 21 Jun 28

21 11.3 21 24.2 21 36.3 21 47.4 21 57.5 22 06.6 22 14.6 22 21.3 22 26.6 22 30.4 22 32.6

-8 05 -9 34 -11 11 -12 58 -14 56 -17 05 -19 27 -22 02 -24 49 -27 45 -30 49

1.811 1.778 1.743 1.709 1.675 1.643 1.613 1.556 1.569 1.556 1.553

1.771 1.813 1.858 1.906 1.956 2.009 2.064 2.239 2.179 2.239 2.300

Date (12hr UT)

R.A. hh mm

Dec. o ’

Delta AU

r AU

Apr 19 Apr 26 May 3 May 10 May 17 May 24 May 31 Jun 7 Jun 14 Jun 21 Jun 28

7 37.7 8 01.0 8 27.3 8 56.9 9 30.7 10 12.3 11 08.4 12 25.3 13 56.4 15 17.9 16 16.4

+71 05 +69 48 +67 39 +63 45 +55 30 +32 22 -27 43 -63 11 -72 52 -75 09 -74 51

0.367 0.312 0.252 0.189 0.127 0.073 0.059 0.105 0.168 0.234 0.302

0.999 0.980 0.970 0.971 0.982 1.003 1.033 1.071 1.115 1.164 1.218

Elong.

Mag.

Const.

9.6 9.4 9.2 9.1 9.0 8.9 8.8 8.7 8.6 8.5 8.4

Boo Boo CVn CVn UMa UMa UMa UMa LMi LMi Leo

122 119 113 105 96 87 78 70 61 53 45

Comet C/2012 X1 (LINEAR) Elong.

Mag.

Const.

72 76 80 85 90 95 101 107 113 119 126

8.8 8.9 9.0 9.1 9.2 9.3 9.4 9.6 9.7 9.8 10.0

Aqr Aqr Cap Cap Cap Aqr Aqr Aqr Aqr PsA PsA

Comet 209P/Linear Elong.

Mag.

Const.

79 76 74 73 73 81 108 120 123 124 126

13.9 13.4 12.9 12.3 11.5 10.4 10.2 11.6 12.9 13.9 14.7

Cam Cam UMa UMa UMa LMi Hya Cru Aps Aps Aps

Positions in these comet ephemerides have been calculated for 12hrs UT (10pm Eastern Australian Standard Time). “Delta” and “r” are the distances of the comet from Earth and the Sun in au.

62 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

This low level of activity, by the way, has also been raised as a caution against northern observers having too high hopes for the expected meteor shower. Nevertheless, an image of the comet obtained by Michael Jager during its 2009 return revealed it as quite an attractive object, like a large comet in

miniature, with a small condensed head and well-defined tail. So it appears that, although feeble, this object is far from being defunct!✦ David Seargent’s ebook Sungrazing Comets: Snowballs in the Furnace is available from Amazon.

AH Scorpii

Alan Plummer

hat you see is not what you get. Depending on various factors we can see with the naked eye around 6,000 stars at best, although at any one time from any one location, it’s a lot less. The most common stars of all, the red dwarfs, are so dim that not one is anywhere near visible to the naked eye. Most uncommon (one in a million) are the red supergiants. Yet we can see 11 with the naked eye! These luminaries can be seen from a long way off. AH Scorpii just misses out of membership of the 11. At maximum it gets to magnitude 6.7, and down to magnitude 9.5, with a period of around 735 days. There have been a couple of maxima I’ve observed with a 50-mm finder

telescope, a valuable scientific instrument. However, AH Scorpii is a semi-regular variable, and a look at the lightcurve since observations began in 1965 shows it capable of doing quite unpredictable things; the amplitude might reduce, period increase or decrease, and so on. All red giants and supergiants are variable. Observation once a fortnight is enough for this slow-moving behemoth, and don’t forget to lodge your data with the AAVSO so it can be used by the wider astronomical community. ✦

96 99 87 86 87 79 60

100 91

The ﬁeld of view (north to south; north is up) is approximately 2o. AH Scorpii (targeted) is located at R.A. 17h 11.3m -32o 20’ AAVSO

Alan Plummer observes from the Blue Mountains west of Sydney and can be contacted at alan. plummer@variablestarssouth.org

Variable Star Maxima 2014

May 2 May 4 May 13 May 15 May 16 May 21 May 30 Jun 3 Jun 5 Jun 13 Jun 15 Jun 19 Jun 25 Jun 27 Jun 29

Star

T Cen S Car R Cae R Vir V CVn X Mon SS Vir RS Sco RU Sgr V Cnc T Her RR Sgr Chi Cyg R Boo S Hya

Mag.

5.5 5.7 7.9 6.9 6.8 7.4 6.8 7.0 7.2 7.9 8.0 6.8 5.2 7.2 7.8

RA hh mm

13 41.8 10 09.4 4 40.5 12 38.5 13 19.5 6 57.2 12 25.2 16 55.6 19 58.7 8 21.7 18 09.1 19 55.9 19 50.6 14 37.2 8 53.6

Dec ’

-33 36 -61 33 -38 14 +6 59 +45 32 -9 04 +0 46 -45 06 -41 51 +17 17 +31 01 -29 11 +32 55 +26 44 +3 04

Listed for each of these long-period variables are the expected date of peak brightness, the star’s typical visual magnitude at peak, and its right ascension and declination. The actual maximum may be brighter or fainter and early or late. COURTESY AAVSO (WWW.AAVSO.ORG).

www.skyandtelescope.com.au 63

Charles A. Wood Exploring the Moon

History of the Moon How do we know when things happened?

The contrast between heavily cratered highlands (bottom) and Mare Humorum demonstrates the rapid decline of impacts prior to about 3.5 billion years ago. JOCELYN SEROT

64 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

lthough the average age of Earth’s surface is only about 500 million years, the oldest rocks geologists have found on our planet formed 3.8 billion years ago. Earth had a rocky crust for 700 million years before then, but it is long gone. Erosion and plate tectonics have erased all of the landforms from the earliest periods of Earth’s history. But you can see another world from your backyard where you can identify features dating from its infancy up to the most recent times. The Moon, like the Earth, Sun, and all other objects within our solar system, ultimately formed from materials that condensed out of the solar nebula roughly 4.5 billion years ago. Its surface was shaped by both external energy (impact cratering) and internal energy (volcanism and faulting). Both processes were vastly more active early in lunar history than they are today. Borrowing a phrase used to describe Earth in the earliest days of its history, the Moon was dominated by “tempestuous tectonics.” Impacts, eruptions, and faulting were everywhere! The immense energy from the countless impacts that brought the stuff together that formed the Moon caused it to completely melt, forming a global magma ocean. Low-density elements such as aluminium floated to the surface as a frothy scum, while denser materials such as iron sank deeper into the molten orb, in a process known as planetary differentiation. The early Moon radiated away its heat rather quickly and began to solidify, though it continued to be punctured repeatedly by a torrent of projectiles — remnants from the solar system’s formation. Over the first 600 to 700 million years, huge impactors collided with the Moon, producing giant basins that are hundreds to more than a thousand kilometres in diameter. Over time, heating due to the radioactive decay of uranium and thorium melted parts of the lunar mantle. This fresh magma rose up

Lunar Impacts and Volcanic Activity

60 10 –1 50 10 –2

10 –3

20 10 –4 10

10 –5

4.5

3.5

2.5

1.5

0.5

Billions of years ago This graph compares the lunar impact rate (shown in blue) with the occurrences of lunar volcanism (red). SOURCE: H. HIESINGER ET AL / JOURNAL OF GEOPHYSICAL RESEARCH 2012

through fractures under the young basins, erupting vast expanses of lava onto the surface. Tens of thousands of eruptions built up the thick, dark flows on basin floors that we see today in Mare Imbrium, Mare Serenitatis, and Mare Crisium. Sinuous rilles, such as Hadley Rille, mark locations where rapidly flowing lavas cut winding channels. This upflow of magma from the mantle to the lunar surface caused the basins to sink, producing fractures around their margins (such as the concentric rilles bordering Mare Serenitatis), and faults in their interiors as the cooled lavas were forced to fit within smaller volumes. About 3.8 billion years ago, impact cratering rapidly declined in both frequency and the size of craters formed. In fact, comparison of the number of impact craters on the lunar highlands with maria ages show that by the time most mare lavas erupted (between 3.8 and 2.5 billion years ago), cratering was thousands of times less frequent as it was during the earlier epoch. Lunar scientists deduced this sequence of events based on the stratigraphic relations of different areas: features that are on top of others are younger than the underlying strata.

Major volcanic eruptions

Cumulatve number of craters (diameter ≥ 1 km, per km2)

To anchor this sequence to a specific time frame, scientists used radiometric dating to measure the absolute ages of samples returned by the Apollo astronauts four decades ago. Unfortunately, these samples were collected from only the six Apollo landing sites. Three more from Soviet Luna samplereturn missions don’t make the collection much bigger. Numerous gaps in our knowledge of lunar chronology are filled with estimates of surface ages based mostly on crater counting. In general, we know that the rate of crater formation in the Moon’s first half-billion years was very high and that the rate quickly declined afterwards, with bumps or spikes over the last 3 to 4 billion years. The exact shape of this cratering curve is debated, so the crater count ages are called “model ages” and are based on combined evidence from the Apollo landing sites, impact rates on Earth, and observations of many asteroids of different sizes. Recently refined crater counts come from high-resolution images returned by NASA’s Lunar Reconnaissance Orbiter (LRO). In fact, you can help contribute to our lunar knowledge by joining the crowd-sourced classification of LRO images at www.moonzoo. org. This ongoing work is leading to a more expansive list of model ages of lava flows, craters, and, most difficult of all, the major impact basins. In truth, this scenario is all a house of cards, but it’s a wellconstructed house, and it’s the best we can do until we bring many more samples from various parts of the Moon back to Earth and study them in laboratories. That is the next major goal of lunar science, but we must return to the Moon to accomplish it. In my next column, we’ll tour the visible clues of lunar history that you can see with your own telescope Ø

Charles Wood (lpod.wikispaces.com) is co-author of the new book 21st Century Atlas of the Moon.

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Exploring the Solar System Thomas Dobbins

When Seeing Isn’t Believing This bright feature in Saturn’s rings is merely an illusion.

n March 14, 1889, an intriguing announcement was issued by the Central Bureau for Astronomical Telegrams in Kiel, Germany, the international clearing house for announcing discoveries and transient events. It reported that Belgian astronomer François Terby had detected a strange new feature in the rings of Saturn. An experienced planetary observer, Terby was widely admired for his studies of Mars and Jupiter. On the evening of March 6th that year, he

was observing Saturn through the 8-inch (20-cm) refractor at his private observatory in the city of Louvain. Using magnifications of 150× to 280×, he noticed a white region bordering the black shadow cast on the rings by Saturn’s globe. Extending across the bright A and B rings, this feature remained stationary for more than an hour until clouds intervened. Six nights later Terby saw the bright boundary again in precisely the same location. A flurry of confirming observations were soon reported, some by

Visual observers are not alone in recording illusory features such as the Terby White Spot, seen in this January 30, 2011 webcam image of the “Dragon Storm” on Saturn by Don Parker.

astronomers using telescopes of only 3 or 4 inches (8 or 10 cm) aperture. Many observers saw Terby’s spot as a bright strip with parallel edges, while to others it looked elliptical or D-shaped, with the flat side of the D’s semicircle defined by the shadow’s edge. William Brooks, the director of the Smith Observatory in Geneva, New York, reported that Terby’s spot “comes

Although the luminance within each of these rectangles is uniform, it seems to vary across the width of each one. Look carefully at the rectangles near the middle and you will see a darker region just to the left (on the darker side) of the edge between two adjacent rectangles and a lighter region just to the right of the same edge. These are Mach bands. If you hold a pencil over any of the boundaries, the apparent difference in the brightness of adjacent rectangles will diminish dramatically.

66 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

out almost conspicuously in the 10inch equatorial [refractor] at times.” Visible with all magnifying powers from 80× to 450×, it was usually most conspicuous with a power of 150×. “To me the brilliancy of the white region appears variable,” Brooks wrote. “Fluctuations of light at irregular intervals of a few minutes have been detected by careful scrutiny.” Despite such corroborating testimony, the Terby White Spot’s lack of motion caused many to immediately question its reality. British amateur astronomer William Noble argued that “the white spot on Saturn’s ring can have no objective existence,” because “the rotation of the ring must carry the luminous patch round and, instead of remaining persistently in contact with the shadow of the ball, it must travel right round the planet.” Andrew Ainslie Common presented compelling evidence that the Terby White Spot is an optical illusion. He reported that when he used a wedge-shaped neutral density filter to gradually attenuate the brightness of Saturn’s image, “the ring disappears at the same time all round, whereas if the white spot had any real existence (i.e. if it were really brighter than other parts of the ring), it would have remained visible after the other portions of the ring had been cut out by the dark wedge.”

The Terby White Spot appears in this 1954 drawing by Thomas R. Cave, who used the Griffith Observatory’s 12-inch (30-cm) Zeiss refractor on a night of excellent seeing. THOMAS A. DOBBINS COLLECTION

We are hardwired to “see” borders even where no contrast exists. Stare at this ﬁgure and you will perceive a white triangle delineated by a well-deﬁned but illusory boundary. GEORGIE FIBONACCI

The human eye-brain combination exaggerates the contrast between light or dark areas at the borders of differing brightness. Common attributed the Terby White Spot to an effect of the stark contrast between the sunlit surface of the rings and the adjacent black shadow of the globe. He noted that an observer can create a spurious, narrow band of increased brightness on any part of the rings (or even the globe itself) simply by placing Saturn partially out of the field of view so that its image is in contact with the eyepiece’s field stop. Another British amateur, J. E. Drower, offered further damning evidence. “I have got a precisely similar appearance to that described by Dr. Terby,” he wrote, “by making a small model of Saturn with a ball and cardboard ring. The latter I nicked on the edge and bent slightly convex until I got a shadow of the ball projected upon it by a strong light.” The Terby White Spot is a striking example of an optical phenomenon first described by the Austrian physicist and empirical philosopher Ernst Mach in 1865. Mach noted that the human eye-brain combination exaggerates the contrast between light or dark areas at the borders of adjacent extended surfaces of differing brightness. Contours and borders dominate human visual perception because edges are accentuated by these features, known as “Mach bands.”

In recent years I’ve encountered remarks posted in online discussion groups alleging that the Terby White Spot must have some basis in reality because it appears in many webcam images of Saturn, often with an uncanny similarity to its appearance in sketches by visual observers. Nothing could be further from the truth. The unsharp masking and wavelet sharpening image-processing algorithms mimic very closely the edge enhancement that occurs in the eye-brain’s neural network. Saturn will reach opposition on May 11th this year. For about 10 days before and after that date, the shadow cast by the globe on the rings will disappear as the Sun, Earth, and Saturn line up. The globe’s shadow will reappear on the following (eastern) side of the ring in late May, and will be widest at quadrature on August 10th, when Saturn is 90° from the Sun. On late autumn and early winter evenings Saturn will be well placed in the eastern sky, affording an opportunity to see the Terby White Spot and answer the old question: “Who are you going to believe, me or your own lyin’ eyes?” Ø

Contributing editor Thomas A. Dobbins observes the planets under the warm, steady skies of Fort Myers, Florida. www.skyandtelescope.com.au 67

Ross Gould Double Star Notes

In the Coils of the Sea Serpent Seek out some of Hydra’s ﬁnest doubles.

ouble stars are prolific in all parts of the sky, and Hydra, the longest constellation, provides a good variety of them. The head of Hydra is in the equatorial sky just east of Procyon, and from there the constellation rambles southeasterly, across the northern border of Centaurus, ending near Libra and Lupus; so it extends over nearly 7 hours in right ascension. This month I've selected some doubles from the middle parts of Hydra, on the northern edge of Antlia and Centaurus. It’s a mix of bright and not-so-bright, the easy and the close, with some objects that might be a challenge. Some of the interesting pairs here are around 8th magnitude, and a curiosity of double star observing is that many amateur astronomers regard an 8th magnitude double as faint and a 9th magnitude galaxy as bright. However even an 80- to 100-mm (3- to 4-inch) telescope will show many of the doubles in this "faint" category, and show them well. There can also be an interest for the observer in testing what is within range of one's telescope and eye; just as galaxy hunters can pursue the faintest of fuzzies, double star observers can pursue close pairs, dim pairs, close unequal pairs, and not limit themselves to the showpieces. Let’s begin with a pair accessible to 80-mm scopes. BU 219 is in an area lacking nearby bright stars, so finding it will be much easier with GoTo or setting circles. For those starhopping, it's about 5½o south-southwest of 3.8-magnitude Mu (μ) Hydrae. Although BU 219 is marked as a double on the Cambridge Double Star Atlas, it's not labelled, which might wrongly suggest it's difficult. Ernst Hartung, in his classic observing book Astronomical Objects for Southern Telescopes, describes it as "well resolved with 7.5-cm". It has hardly changed since Sherburne Wesley Burnham found it with his 6-inch (15-cm) refractor in the 1870s (a slightly different 1874 measure appears to be inaccurate). Common proper motion suggests a long-period binary. I observed BU 219 some years ago with an 18-cm (7-inch) refractor, and at only 100x it was a fine, uneven, fairly close pair; the stars bright; and the colours appearing as Hartung calls them, "pale yellow and white". Another 5o southeast from BU 219 is our orbit diagram pair, BU 411, itself ¾o north-

The apparent orbit of BU 411

-0.5

1946 -1.5

-1

-0.5

0.5

East

2082

0.5

2048

1980

2014

North

northwest of an orange 5th magnitude star. BU 411 is offset from the end of a line of 9th – 11th magnitude stars. Another of Burnham's 1870s discoveries with his 6-inch refractor, this one has shown considerable orbital motion since discovery and has a calculated period of 170 years. The stars are bright, and the current separation places the pair at the Dawes Limit for 90-mm (3.5-inch) telescopes, so with 80-

mm aperture it will likely only be elongated, and with 100-mm barely split. In the 18-cm refractor a few years ago it was a neat, slightly uneven pair, the yellowish stars just apart at 180x. Back around 1950 the minimum separation was only 0.15", though it rapidly increased to 0.6" by 1961. It has continued to widen, and will reach maximum (1.4") in the 2020s. Closing after that, it will still be 1.0" apart at the beginning of the 2070s.

Double Highlights in Hydra Star Name

SHJ 110

Right hh mm

Declination Magnitudes

10 04.0

-18 06

o '

BU 1072

Separation Position Date of Spectrum (arcseconds) Angle(o) Measure

AB 6.2, 12.1

12.6"

052

2000

AC 6.2, 7.0

21.2"

274

2011

B8V

BU 219 BU 411 STF 1474

10 21.6 10 36.1 10 47.6

-22 32 -26 41 -15 16

6.7, 8.5 6.7, 7.8 AB 6.7, 7.0 BC 7.0, 7.6

1.8" 1.3" 67.8" 6.3"

186 306 028 018

1996 2013 2012 2012

A1V F6V B9IV

STF 1473

10 47.6

-15 38

AB 7.7, 8.9 AC 7.7, 10.4

30.4" 97.9"

010 332

2012 2000

F7II/III

I 211 HWE 25 N Hya (H 3 96) HJ 4455 I 232 HJ 4465 Beta Hya (HJ 4478)

10 59.2 11 03.3 11 32.3 11 36.6 11 40.0 11 41.7 11 52.9

-33 44 -27 31 -29 16 -33 34 -33 27 -32 30 -33 54

5.8, 9.5 7.7, 9.6 5.6, 5.7 6.0, 7.8 7.0, 10.1 AC 5.4, 8.3 4.7, 5.5

1.9" 2.8" 9.4" 3.4" 2.2" 67.2" 0.7"

220 342 210 241 161 043 037

1991 1991 2007 1991 1991 2009 1998

F2V A1/2V F8V, F8V K0III K1III K5III, F7V B9III

Data from the Washington Double Star Catalogue

68 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

Northward from this area there are several pairs. SHJ 110 shows in small telescopes as an attractive easy pair of bright white stars. That's how Sissy Haas describes it in her book Double Stars for Small Telescopes, as seen with a 125-mm (5-inch) refractor at 50x. But a little more aperture brings a third star into view. The 18-cm refractor I used showed the fine bright pair at low power, and increasing the power to 180x brought into view the tiny speck of Burnham's later-discovered and closer 12th magnitude companion (BU 1072). The SHJ pair was part of the early1800s harvest of doubles by James South and John Herschel, found with small telescopes. About 1o north and a little west from 3.1-magnitude Nu (ν) Hydrae is STF 1474, an attractive triple in a nearly straight line. This is a very wide 7th magnitude pair, nearly north-south in orientation, with a slightly fainter near companion to the northern star. Haas remarks on the bright orange Nu Hydrae being in the field (presumably a very wide field!), and there's a broad triple star on the way to Nu Hydrae, STF 1473, a third of a degree south of STF 1474. A 100-mm scope will show all this nicely. Moving well south now, we'll visit one of Robert Innes's doubles, discovered with a 7-inch refractor in 1897 from the Cape Observatory, South Africa. Since discovery, I 211 has slowly widened a little with increasing angle, though there's not yet enough of the orbit traced out to enable calculating it. With the 18-cm refractor at low power, I 211 was a bright yellowish star in a faint field, and the close and much fainter companion became visible at 180x. With a brightness difference of 3.7 magnitudes, at 1.9" separation, I'd expect this pair to be testing for 10- to 13-cm telescopes, and it will need good air steadiness. Northwards 7o, and just west of 5th magnitude Chi1 (χ1) and Chi2 Hydrae, is HWE 25. This unequal pair of slightly yellowish stars showed double at 100x in the 18-cm refractor, and 180x made it easy and obvious. 100-mm aperture will show it fairly well, though the secondary star is not bright at magnitude 9.6. N Hydrae (H 3 96) is a bright, easy, and very fine pair, some 2½o north from 3.5-magnitude Xi (ξ) Hydrae. Haas with a 60mm (2.4-inch) refractor calls the star colours "grapefruit orange". I saw the stars as yellow, as did Hartung, who also noted an "orange red star" nearby. From here, move south of Xi Hydrae to a gathering of 6th magnitude stars which includes another bright double, HJ 4455. The deep yellow stars form a pair which Hartung called "beautiful", commenting that it was "a

fine object for 7.5-cm". With the 18-cm refractor it was a clear and attractive, unequal pair at 100x. Some 40’ nearby to the east is the fairly difficult pair I 232, stars of magnitudes 7 and 10 at 2.2". Again, a deep yellow primary, the companion is a close little point of light visible with 180x through my 18-cm refractor. A degree north and just east of I 232 is HJ 4465. This shows as a very wide, uneven double at low power. Visible with 60-mm aperture are two 5th and 8th magnitude stars, orange and yellow respectively. Each of the stars has a 13th magnitude companion requiring large apertures — 30" away for star 'A', and close (4.5") and hence very difficult for star 'B'. We’ll conclude with the close but striking pair Beta (β) Hydrae (HJ 4478). It's a John Herschel discovery from 1834, when the stars were at an easy 2" separation. Since then it's gradually closed with increasing angle. Hartung found in 1961 that 15-cm aperture just separated the stars, at the time nearly 1.0" apart. When I observed it 40 years later with

the 18-cm refractor, the pair was closer, 0.7", and I did not get a clean separation. At 180x there was a slight elongation; at 330x it was an uneven figure-8 shape. The pair appeared to be entering the closest and fastest-moving part of its orbit in the 1990s. I've not looked at it recently, but the current separation might still be close to 0.7". However the angle will have increased, perhaps to as much as PA 60R. The pale yellowish stars are only slightly unequal in brightness. New observations will indicate if Beta Hydrae has begun to widen again or has stayed very close. I'd suggest telescopes of 20cm or greater. Beta Hydrae is not a nearby double, with an Hipparcos-derived distance of around 360 light-years. The orbit has not been calculated yet, but it will be large — the early measure of 2.0" is around 224 au in projection; even 0.7" is 78 au. ✦ Ross Gould has been a long-time double star observer from the suburban skies of Canberra. He can be reached at rgould1792@optusnet.com.au.

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Sue French Targets

The Realm of the Nebulae Some unusual galaxies lie near the Virgo Cluster’s eastern edge.

“T

he universe is empty, for the most part, but here and there, separated by immense intervals, we find other stellar systems, comparable with our own. . . . These huge stellar systems appear as dim patches of light. Long ago they were named ‘nebulae’ or ‘clouds’ — mysterious bodies whose nature was a favourite subject for speculation.” American astronomer Edwin Hubble penned these words in the first chapter of his 1936 book The Realm of the Nebulae. Hubble sided with tradition, calling these distant stellar systems extragalactic nebulae, but today they’re more commonly known as external galaxies. When amateur astronomers think of the Realm of the Galaxies, the area of the sky dominated by Virgo and Coma Berenices quickly comes to mind. This region holds the north galactic pole, one of the two spots in the sky farthest from the dust-laden plane of our galaxy’s disk. Here we have a clear window into the depths of the universe, where we can view distant galaxies unobscured by the Milky Way. Let’s explore some lesser-known galaxies on both sides of the boundary between Virgo and Coma Berenices within a few degrees of the deep yellow star Epsilon (ε) Virginis, also known as Vindemiatrix. We’ll start our galaxy tour with a hop 2.5° northwest from Vindemiatrix to 41 Virginis, and then jump 1.8° in the same direction to 28 Comae Berenicis. The star 28 Comae Berenicis sits 14′ south-southeast of NGC 4689, and they make a lopsided box with two relatively bright stars to the galaxy’s south and southwest. The box nicely fits within a low-power field of view. Through my 130-mm refractor at 37×, NGC 4689 is a fairly dim eddy of mist filling a plump oval, tipped northnorthwest, and harbouring a somewhat brighter core. A faint star watches the galaxy’s north-northeastern side, and at 117× it’s accompanied by a dimmer sentry. The higher magnification also

The blue areas in this image of the spiral galaxy NGC 4689 are regions of recent star formation. SLOAN DIGITAL SKY SURVEY

70 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

makes NGC 4689 look vaguely woolly, with a ¾′-long, oval core and a 2½′ halo. NGC 4689 is roughly 58 million light-years away, in the outskirts of the Virgo Cluster. In deep images, this galaxy shows a fleecy inner disk with ongoing star formation that abruptly gives way to a diffuse outer disk. Studies indicate that the outer disk’s lack of star birth is due to gas being stripped away by the hot intracluster medium. The star 29 Comae Berenicis lies 27′ northeast of NGC 4689, and climbing 1.1° north from there takes us to NGC 4710. The galaxies share the field in my 130-mm scope when I use a wide-angle eyepiece that gives me 37× and a true field 2.2° across. NGC 4710 is moderately faint and very elongated, leaning northnortheast. A 12.6-magnitude star

rests 1.5′ east of the galaxy’s centre. The double star Struve 1678 (Σ1678 or STF 1678) also inhabits the field of view, making a right triangle with the two galaxies. The 7.2-magnitude white primary is widely separated from the 7.7-magnitude yellow companion that dangles to its south. At 117×, NGC 4710 covers about 4½′ × 1′ and hosts a large, elongated core that brightens toward the middle. A second double star can just be crammed into the 2.2° field, but it puts on a better show when centred. Struve 1686 gifts us with a fine, nearly matched, yellow-white pair of 9th-magnitude suns, the primary closely guarding its companion to the south. The two stars show a fairly wide separation through the telescope at 63× and look like the gleam of two little eyes watching us from the depths of space.

Targets

Above: NGC 4710 is unusually dusty for a lenticular galaxy. North is to the upper left in this image from the Hubble Space Telescope. NASA / ESA Below: This beautiful image of NGC 4866, a more typical lenticular galaxy, was retrieved from the Hubble Legacy Archive and placed in Wikimedia Commons. NASA / ESA / STSCI

Star magnitudes

13h 10m

13h 00m

12h 50m

+16° 5 6 7 8 9 10

4758

COMA BERENICES

Σ 1686

4866

+14°

IC 3806

Σ 1678

Σ 1705

4935

4710

4969

4689

VIRGO 5058

4880

5020

41 4746

+12°

4992

72 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

4754 4762 4733

4660 4694

NGC 4710 is an S0 (lenticular) galaxy with half the stellar mass of our Milky Way Galaxy. It’s about 55 million light-years distant, in the outlying regions of the Virgo Cluster. NGC 4710 has a dusty disk, which is puzzling. An S0 galaxy’s dust ought to be quickly eroded away by impacting ions in the galaxy’s “atmosphere.” Although dust might be replenished by unexpectedly high rates of star formation, a 2010 study by Yuanyuan Su and colleagues suggests that dusty S0 galaxies simply lack the atmospheres of hot, X-ray-emitting gas found in most S0s. The authors studied three edge-on S0 galaxies with dusty disks, including NGC 4710, and found that their ratios of X-ray to optical luminosity are among the lowest known for S0 galaxies. NGC 4866 is another outer Virgo Cluster member, but this one is 78 million light-years away from us. Look for it 2.6° east of 29 Comae Berenicis. Through my 130-mm refractor at 37×, the galaxy is a nice, highly elongated, east-west streak that grows brighter toward the centre. Just 23′ to the east-northeast, the wide double Struve 1705 shares the field of view. Its 9th- and 10th-magnitude components are widely split, shining pale yellow and yellow, respectively. At 117× the galaxy appears about 5′ long with an elongated 3′ core and a small, bright centre. The core wears a faint star on its northern flank roughly halfway from the galaxy’s centre to its western tip. We can reach NGC 4880 by dropping 1.7° south from NGC 4866 or by working our way 1.6° northnorthwest from Vindemiatrix. In my 130-mm scope at 63×, it’s just a small, very faint fuzzspot that’s considerably easier to see with averted vision. At 117× the galaxy displays an oval glow leaning west of north. Through my 10-inch reflector at 213×, NGC 4880 grows gently brighter toward the centre, and its diaphanous halo covers about 2′ × 1¼′. A very faint star neighbours the galaxy’s southsoutheastern edge, and an orange 9.8-magnitude star rests 11′ southeast of its centre. NGC 4880 is about 51 million lightyears distant and may be related to other galaxies in the Virgo Cluster’s outskirts. But our final galaxy, NGC 5020, lies well beyond the Virgo

Cluster at a distance of 160 million light-years. The face-on spiral galaxy NGC 5020 sits 3° east of NGC 4880 and the same distance away from Vindemiatrix. It makes a straight line with two yellow-orange stars (magnitude 8 and 9) to the westnorthwest. The line is 29′ long, and the three objects are evenly spaced. NGC 5020 is a very faint touch of haze with a moderately brighter centre as seen with my 130-mm refractor at 37×. Boosting the magnification to 117× reveals a dim, roundish halo spanned by a brighter, nearly north-south glow that has a small, relatively bright core. Although

my 10-inch (25-cm) scope at 166× brightens and clarifies the image, it reveals no further details except for a starlike nucleus. NGC 5020 is a photogenic galaxy with striking spiral arms. It’s morphological type is SAB(rs)bc. The S tells us that this is a spiral galaxy, AB signifies its weak bar, rs denotes the broken pseudo-ring that the bar spans, and bc indicates that the galaxy has fairly open spiral arms and a small but obvious central bulge. According to a 2010 study by Sébastien Comerón and colleagues, NGC 5020 also has a tiny, star-forming nuclear ring only 8.6″ in diameter. On most images, this ring is lost in the galaxy’s overexposed core. NGC 5020 also played host to a Type II supernova in 1991. Only three images of it were taken. At discovery, it had a red magnitude of 17. It had faded in the two subsequent images, taken 48 and 105 days later. A Type II supernova is caused by the core collapse of an aging, supergiant star. The outer layers of the star explode outward, while the crushed core usually becomes a neutron star. A typical neutron star is only 10 kilometres across, but if you packed a box that’s one metre long on each side with neutron star stuff, it would weigh 100 trillion tonnes. ✦

NGC 5020, a spiral galaxy with a weak bar and broken ring, looks strikingly like a miniature version of Messier 61. SLOAN DIGITAL SKY SURVEY

Object

Type

Magnitude

Size/Sep.

Dec.

NGC 4689

Galaxy

11.0

4.3′ × 3.5′

12h 47.8m

+13° 46′

NGC 4710

Galaxy

11.0

4.9′ × 1.2′

12h 49.6m

+15° 10′

Σ1678

Double star

7.2, 7.7

37″

12h 45.4m

+14° 22′

NGC 4866 Σ1705

Double star Galaxy Double star

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Orion® HDX110 EQ-G GoTo Equatorial Mount with Tripod Pier #10011

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Sue French welcomes your comments at scfrench@nycap.rr.com.

Galaxies & Double Stars near the Virgo-Coma Border

Σ1686

Since

1975

8.6, 8.7 11.2 9.0, 10.3

5.7″ 6.3′ × 1.3′ 27″

+15° 02′

+14° 10′

+14° 23′

12 53.0 12 59.5 13 00.8

NGC 4880

Galaxy

11.4

3.2′ × 2.3′

13 00.2

+12° 29′

NGC 5020

Galaxy

11.7

3.2′ × 2.7′

13h 12.7m

+12° 36′

Orion® Atlas™ Pro AZ/EQ-G Computerized GoTo Mount #10010

Orion® Sirius™ EQ-G Computerized GoTo Mount #24336

Angular sizes and separations are from recent catalogues. Visually, an object’s size is often smaller than the catalogued value and varies according to the aperture and magniﬁcation of the viewing instrument. Right ascension and declination are for equinox 2000.0.

OrionTelescopes.com www.skyandtelescope.com.au 73

Steve Gottlieb Going Deep

Digging Deep in Messier 83 This magniﬁcent spiral galaxy is best observed from southerly latitudes.

83, the gorgeous Southern Pinwheel, ranks high on my all-time favourites list. Shining at magnitude 7.5, M83 is the 4th-brightest Messier galaxy after M31, M33, and M81. And at a distance of 15 million light-years, it’s one of the nearest “grand-design” barred spirals. M83’s spiral arms are bursting with pink star-forming regions and recently minted blue star clusters. A 1983 catalogue in the Astrophysical Journal lists 298 H II regions — sites where young, massive stars have ionised nearby gas clouds. M83’s central bar

In 1787 William Herschel trained his 18.7-inch (47.5-cm) speculummetal reflector on M83 from his garden in England. Although the galaxy was just 10° above the horizon, he noted “faint branches about 5′ or 6′ long, elongated southwest to northeast.” Searching for clear, transparent skies, British amateur astronomer William Lassell shipped his 48-inch (1.2-metre) equatorial reflector to Malta in 1861. He described it as a “three-branched spiral” and producing the sketch shown on the following page.

funnels gas into a starburst nucleus, which harbours numerous massive stars. This activity has produced six supernovae in the past 90 years, a record only surpassed by NGC 6946. French astronomer Nicolas-Louis de Lacaille discovered M83 during his expedition to the Cape of Good Hope in 1751–1752. Using just a half-inch refractor at 8×, Lacaille catalogued 9,766 southern stars along with 42 nonstellar objects (mostly clusters). He logged M83 as a “small, shapeless nebula” and included it in his list of nebulae “not accompanied by any star.”

11 10

8 7 9 6 4

Some of the major H II knots in M83’s spiral arms are labeled in this European Southern Observatory photograph.

74 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

ESO

Its counterpart begins on the bar’s southwest end and shoots north before curling eastward along the north side. The third arm branches outside to the south and curves west.

Your best view will be on a dark, transparent night when M83 is at its highest... In 2008 I travelled to Zane Hammond’s Magellan Observatory near Lake Bathurst in New South Wales and viewed M83 in his 24inch (61-cm) f/3.7 scope while it was directly overhead. At 200× the bar extended 3′ × 1′ and enclosed a bright circular nucleus. The two prominent arms appeared chiselled with high contrast by dust lanes at their edges. The longer northern arm winds roughly 270°, merging into the halo on the southeast side near the 8″-wide double star h4599, whose components shine at magnitude 10.5 and 11.5. The southern arm attaches at the northeast side of the bar, sweeps south and west, and peters out 3′ south of centre.

A 48-inch reﬂector and an observing site at latitude 35° north enabled William Lassell to discern M83’s spiral structure in 1862.

Spica

1 Star magnitudes

M83 lies in southern Hydra, 19° south of Spica, at declination –30°. So mid-northerners like myself often observe M83 through the haze and light pollution that tend to hug the horizon, making it tough to see more than its bright core. But given the right conditions, M83 is rich in detail, with 8- to 10-inch (20- to 25-cm) scopes revealing the central bar and spiral arms, and larger apertures resolving multiple H II knots and dark rifts. I first observed M83’s spiral structure through my 13-inch (33-cm) solid-tube reflector in the early 1980s. I saw a weak central bar running northeast to southwest, punctuated by a small, bright core. The two principal arms weren’t easy, but they nearly merged to form the Greek letter theta (θ). Not bad from Northern California, but I knew I was missing out on the real deal. In February 2004, I lugged a 13inch airline-portable travelscope to the Costa Rica Southern Sky Party, which is held annually at a dark site along the Gulf of Nicoya. From a latitude of +10° north, M83 rose 50° above the horizon, and the detail now popped! Three spiral arms were separated by darker ribbons of dust and embedded within an 8′ × 6′ halo. The arm attached to the northeast side of the bar unfurls counterclockwise around the south side of the galaxy.

When I increased the magnification to 375×, several small knots sparkled near the inner ends of both arms, and darker veins of dust sliced across the arms. Last year I scrutinised M83 in Texas through Jimi Lowrey’s 48-inch jumbo-sized Dob, and the arms were chock-full of glowing H II regions. The brightest of these are marked on the photograph on the facing page. At 488× I saw three prominent knots (#1–3), varying in size from 10″ to 20″, at the northeast end of the central bar. A series of fuzzy splotches was symmetrically placed on the opposite side (#4–8), with the largest splotch extending 25″. And I saw additional bright clumps at the southwest (#9) and northeast (#10–12) sides of the halo. To view M83 in its full glory — along with the many other showpieces of the far-southern sky — observers in the Southern Hemisphere are in prime position. But from any location, your best view will be on a dark, transparent night when M83 is at its highest on the meridian Ø S&T contributing editor Steve Gottlieb has made several trips to the Southern Hemisphere to complete his observations of the New General Catalogue of Nebulae and Star Clusters.

–10°

M104

VIRGO

3 4 5 6 7

d b

CORVUS a

–20°

¡ _

M68

HYDRA 14h

M83

13h

12h

–30°

www.skyandtelescope.com.au 75

Gary Seronik Telescope Workshop

The Jones Medial Refractor This optical design builds on the strengths of several previous ones.

elescope making is a hobby with many facets. Some people enjoy assembling scopes with commercial parts, whereas others want to make everything from scratch. And there are also the adventurous ones such as Ed Jones of Ohio who enjoy creating new designs. I featured Ed’s Chiefspiegler reflector in the February/March 2009 issue, page 84. His newest effort is a highperformance design that he calls the Jones Medial Refractor. It builds on some of his previous scopes, including the Chiefspiegler, and it also shares DNA with exotic designs such as the Schupmann and Honders/Busack Medial refractors. “When developing this design,” Ed says, “I started with the Honders/Busack Medial, but I tilted the lenses to avoid an obstruction, and I used Chiefspiegler-type correctors.” Ed’s scope has a single-element, 7-inch (17.8-cm) objective (made from BK7 or K5 optical glass). The next element in the optical path is a 6.66inch (16.9-cm) diameter Mangin

Field lens

Focal plane

The Jones Medial Refractor

S&T: LEAH TISCIONE

Relay mirror

Objective lens

Ed's 7-inch is just one possible variant of the design; his recipe can be modiﬁed to produce other examples that retain its excellent performance.

Ed Jones shows off his 7-inch Medial refractor that features apochromatic performance. ED JONES

76 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

corrector — a lens whose back surface is aluminised (or chemically silvered in Ed’s case) to reflect light back through the lens a second time. As such, it functions as both a lens and a mirror. The Mangin corrects for the chromatic aberration of the single-element objective. In Ed’s design, the Mangin is tilted to divert the light cone toward the side of the tube, thus avoiding the need for an obstructing secondary mirror. But, as is typical in the optical-design game, the solution to one problem often creates a new one. In this case, the new problem is a tilted field. “To correct for this, I changed the folding element from a [5.56-cm] flat mirror to one with a very weak convex curve,” Ed says. “The result is a telescope that is highly corrected, like the Honders, but unobstructed.” Light from the convex mirror is fed through a 2-inchdiameter plano-convex field lens that corrects for lateral colour error and astigmatism. This is an off-the-shelf

Mangin corrector

component (part number 011-4660) from OptoSigma (optosigma.com) Ed’s scope has five optical surfaces (excluding the field lens), each of which must be generated, polished, and tested. That sounds like a lot of work, but all the surfaces are spherical, which makes the task considerably easier. The extra effort does, however, pay off. The resulting telescope is compact, features a convenient eyepiece position, and most importantly is a superb performer. “The scope works very well at high magnification with no hint of colour error,” Ed reports. “It puts a lot of dark sky between all four of the components in Lyra’s famed Double Double. I also enjoy using a low-power eyepiece and seeing perfect star points all the way out to the edge of the field.” Ed’s 7-inch is just one possible variant of the design; his recipe can be modified to produce other examples that retain its excellent performance. For instance, Ed says that with some changes to the focal ratio and the spacing of elements, the design can be scaled up to a 40-inch (1-metre) scope and still be diffraction limited across the entire visible spectrum! Readers interested in exploring the Jones Medial Refractor further can obtain detailed information by e-mailing Ed at opticsed@gmail.com ✦ Contributing editor Gary Seronik is an experienced telescope maker. He can be contacted through his website, www.garyseronik.com.

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Less Is More

Stargazing Simpliﬁed FRED ESPENAK

A small scope at medium-low power has boundless potential.

las! Today’s hectic lifestyle, obsession with electronic gadgets, and the mantra that “bigger is better” have carried over into amateur astronomy. Witness the Messier Marathon, computer-controlled remote CCD-imaging telescopes, and observatory-sized, trailer-mounted Dobsonian reflectors (page 88). Casual, relaxing stargazing seems to be largely a thing of the past — something practiced by only a few purists. To me, stargazing should provide a relaxing interlude from the pressures and worries of everyday living rather than contributing to them. I’ve been privileged to use some of the largest telescopes in the world, including a 30-inch (76-cm) Brashear refractor. While the views in giant scopes can

A spotting scope is perfect for viewing the Moon near the horizon, where atmospheric distortion would disrupt the view in a larger telescope.

JAMES MULLANEY

78 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

certainly be awesome, my most enjoyable stargazing sessions have been with very small instruments. As an example, I’ll share some of the exciting celestial sights I continually enjoy on clear nights using a basic 3-inch (7.5-cm) achromatic spotting scope intended for nature study such as bird watching. It has a fixed magnification of 30× — no fiddling with eyepieces in the dark or deciding which to use. Its field of view is 100′.. That may seem modest in this age of fast apochromatic refractors and wide-field 2-inch eyepieces, but it’s ample to frame many of the sky’s best vistas. With its simple tabletop alt-azimuth mount and a total weight of around 2 kilograms, my spotting scope is always

JAMES MULLANEY (2)

ready for instant use; no cool-down time needed! Being a refractor with an unobstructed light path, its images are razor sharp. And the views are virtually unaffected by poor atmospheric seeing due to the scope’s small aperture and low magnification. For more prolonged sessions, I also use it on a vintage Unitron alt-azimuth mount with slowmotion controls and a tripod with wooden legs, which are far superior to metal legs at damping vibrations. This little glass has yet another virtue over big ones: it has a relatively limited number of targets. You might not consider this an advantage — but it is! I’m not tempted to find large numbers of objects every time I go out, eliminating the malady I refer to as “saturated stargazing.” Astronomy writer Michael Covington tells us that “All galaxies deserve to be stared at for a full 15 minutes.” I would extend this advice to every celestial object. I prefer to view at most a dozen of the sky’s wonders (including the Moon and planets) during the course of an evening in a relaxed and contemplative manner. To me, glancing at an object, then rushing on to another and another is like reading the CliffsNotes of the world’s great novels. Here are some of the celestial sights that I enjoy most through the small spotting scope from the Northern Hemisphere. The Moon. Those who have ever only looked at our lovely satellite close up with high magnifications are

surprised and delighted at its crystalline appearance at 30×. Lunar eclipses are at their absolute best at such a magnification, which bridges the gap between typical telescopic and binocular views. So too is earthshine, the “new Moon in the old Moon’s arms,” which seems more intense in this little scope than in other instruments. And for the ultimate thrill, I watch lunar occultations of other sky targets, especially planets or large star clusters such as the Hyades. The Moon appears suspended in threedimensional space as it glides across a cluster, covering and then uncovering individual stars, making its slow eastward orbital motion a joy to watch. Planets. Several of the planets look positively jewel-like magnified just 30 times! Venus when in its crescent phase a month or two before and after inferior conjunction is one example — a tiny, radiant silver sliver hanging in the sky. Jupiter has to be one of the grandest and most thrilling sights in the heavens. The endless dance of the Galilean moons about the planet, continually changing position and configuration, never loses its fascination. Watching the satellites disappearing in front of or behind the planet’s disk, or passing in or out of its shadow, is like watching a celestial fourring circus! And then there’s Saturn, the supernal wonder of celestial wonders, the iconic image of astronomy, the most otherworldly object in the heavens. The spectacle of the rings hugging the planet,

Many widely spaced double stars appear more impressive in small telescopes at low magniﬁcations than in big scopes. Colourful Albireo, shown here, is a prime example. JOHANNES SCHEDLER

just barely resolved at 30×, looks too beautiful and ethereal to be real! Comets. My little scope is ideal for viewing bright comets, its wide field typically taking in the entire object — nucleus, coma, and tail. It’s also superb for including other objects in the same view, which sometimes makes it possible to see the comet’s motion in a matter of minutes. Double stars. My favourite deepsky targets in the 3-inch glass are double and multiple stars. Literally thousands can be split even in such a small aperture. Many people’s favourite is

Planets are wonderful to view in detail, though no Earth-based telescope can rival this Hubble Space Telescope view of Saturn. But they have a different kind of beauty when magniﬁed just enough to make the main features visible, as in the inset image. NASA / HUBBLE HERITAGE TEAM / STSCI / AURA

www.skyandtelescope.com.au 79

Less Is More magnificent Albireo (Beta Cygni). Its topaz-orange and sapphire-blue hues are magnificent, with the components separated just right at 30×. But this jewel is basically a winter and spring target. A great substitute in late summer is h3945 in Canis Major. And moving into autumn, there’s also Iota Cancri. Living in the Northern Hemisphere, I’ve christened them the Winter Albireo and Spring Albireo, respectively, and both of these clones are beautiful sights in the smallest of telescopes. Another favourite target for me in the Northern Hemisphere is wide Mizar and Alcor at the bend of the Big Dipper’s handle, with Mizar itself neatly resolved into blue-white gems at 30×. Most readers have viewed the stunning quadruple Theta1 Orionis — better known as the Trapezium — at the heart of the magnificent Orion Nebula.

At 30×, the stars in this tight knot appear nearly in contact with one another! At the other extreme, the sky contains many widely separated pairs that look like unrelated stars in a large telescope and appear to best effect in a small glass. One example is Omicron1 Cygni, the sky’s widest beautiful triple system. It displays striking contrasting hues of orange, white, and blue at low power, but the effect disappears as magnification increases and the components become unduly separated. Star clusters, asterisms, and associations. The magnificent

Pleiades in Taurus and Beehive Cluster in Cancer are perfect matches for my little glass, filling its field of view. The grand Double Cluster in Perseus (another Northern Hemisphere sight) is a dual starburst against a rich Milky Way field.

Although globular clusters need larger scopes to appreciate their full magnificence, these fuzzy starballs look remote and mysterious at 30×. And some of the brighter ones, such as M13 in Hercules and M22 in Sagittarius, sparkle when viewed with averted vision.. And then, in the far south lie Omega Centauri and 47 Tucanae... Finally, there are truly expansive stellar groupings such as the Alpha Persei Association and big asterisms like the Coathanger (Collinder 399) in Vulpecula, both of which are amazing in a wide field at 30× or less. Nebulae. Sure — everyone has seen the magnificent Orion Nebula before. But have you viewed the entire complex? In addition to M42 and M43, it includes the sparse open cluster NGC 1981 to the north and the two neighbouring double stars Iota Orionis and Struve 747 just to the south — all of which can be seen in a single eyepiece view at 30× on the 3-inch. Again, most readers have seen the Lagoon Nebula (M8) and Trifid Nebula (M20) in Sagittarius — but have you seen them together in same eyepiece field, as I can in my spotting scope? Diffuse nebulae aren’t the only nebulous attractions — we also have planetaries. Everyone’s favourite, the Ring Nebula (M57) in Lyra, looks like a

LORENZO COMOLLI

ADAM BLOCK / NOAO / AURA / NSF

AKIRA FUJII

Left: The open cluster Messier 44, in the centre of this photo, tends to appear like a group of unrelated stars when viewed at high power. Lower left: M31, the Andromeda Galaxy, makes an incredible wide-ﬁeld tableau with its satellites M110 (top) and M32 (bottom). Below: Cigar-shaped M82 and the huge spiral M81 form the brightest galaxy pair in the sky.

80 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

Since

1975

Everything for the Amateur Astronomer

ASTROPHOTOGRAPHY

AKIRA FUJII

tiny elliptical donut, with the central hole just visible using averted vision at 30×. Seeing it just barely resolved is quite thrilling! The Dumbbell Nebula (M27) in Vulpecula is much bigger and more obvious, looking like a little pillow floating among the rich Milky Way background. And a third type of nebulosity is represented by the Crab Nebula (M1) in Taurus. I can spy this supernova remnant easily in the 3-inch, and although it’s small at 30×, its elliptical shape is obvious. Galaxies. This entire article could easily be devoted to the galaxies visible in a 3-inch glass. At the top of the list is the magnificent Andromeda Galaxy (M31) and its two dim companions, M32 and M110. Not only do all three fit in the same eyepiece, but the main galaxy itself extends far beyond my scope’s wide field of view in opposite directions. Sweeping back and forth across this wonder of the great beyond on a dark night is thrilling beyond words. Other favourites with my little glass are the Triangulum Galaxy (M33), the Sombrero (M104) in Virgo, and the big Sculptor Galaxy (NGC 253). From the Northern Hemisphere, there is also Bode's Galaxies (the M81/82 pair) in Ursa Major and the Whirlpool (M51) in Canes Venatici, and deep in the south are the Magellanic Clouds! All of these island universes are alluring sights in the 3-inch and have a decidedly remote look to them at just 30× — unlike the close-up views at higher powers.

The Milky Way. Saving the best for last, the grandest object in the entire heavens is our own Milky Way Galaxy! Sweeping its massed star clouds at low power is an exhilarating experience — especially those of winter in Cygnus, Scutum, and Sagittarius. This is truly Downtown Milky Way! And while the summer Milky Way isn’t as rich and obvious in those months, it’s still a starry wonderland in constellations such as Cepheus, Cassiopeia, Perseus, Auriga, and Puppis. And in the far south there's the vast band of Carina and Vela! Whatever part of this Great White Way of the heavens you choose to view, be alert to an amazing illusion — one that favours low-power, wide-field views, and is actually at its best in binoculars. As you stare into a particularly rich star cloud, note that the brighter stars appear closer to you than the fainter, more distant ones behind them. As the eye-brain combination makes this connection, a sensation of 3-dimensionality can occur, causing the Milky Way to jump right out of the sky at you! It’s always been a rule of thumb in stargazing that the smaller the telescope, the more often it will be used. Part of that relates to weight and portability. But as the above discussion clearly demonstrates, there’s certainly more involved here than size alone! ✦ James Mullaney’s latest book is Celebrating the Universe!: The Spirituality & Science of Stargazing.

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Orion® StarShoot™ 5 MP Solar System Color Camera #52097

Orion® StarShoot™ All-In-One Astrophotography Camera #52098

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OrionTelescopes.com www.skyandtelescope.com.au 81

Astrophotography

Red Luminance Layering Boost the nebulosity in your astrophotos with this novel technique.

n recent years, DSLR and one-shot colour (OSC) CCD cameras have surged in popularity with astrophotographers. The sensitivity and noise levels in these camera designs have improved to the point that serious imaging is no longer solely the province of dedicated monochrome CCD cameras with colour filters. However, because of the very nature of the DSLR and OSC permanently filtered detectors, it’s difficult to do the specialised imaging involved in narrowband enhancement of nebulae and other objects. Fortunately, you can boost the nebulosity recorded with these cameras by using the red luminance layering technique. This method doesn’t require any additional filters. I prefer to image with an OSC camera because it allows me to capture colour images in a single exposure. This saves

EDWARD HENRY

82 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

me the expense of having to buy filters and a filter wheel. It also ensures that every time I shoot, I’ll automatically have an exposure in every band: unexpected clouds or equipment failures don’t interfere with my ability to capture a full set of red, green, and blue images, as can sometimes occur when imaging with monochrome cameras. But often I find that my result lacks the impact of a comparable image recorded using a monochrome camera with colour and narrowband filters. To combat this problem, I’ve developed an easy technique to enhance my images by layering in new data and mixing the colour channels using the software ImagesPlus (www.mlunsold. com). ImagesPlus was written specifically for processing astrophotos from OSC and DSLR cameras as well as standard monochrome CCD cameras.

Left: In this one-shot colour (OSC) image, it’s difficult to see hydrogen nebulosity in the outer regions of the Helix Nebula (NGC 7293). Right: Creative mixing of the red channel with the other colour channels and luminosity in the image makes these faint wisps much more apparent. ALL IMAGES ARE COURTESY OF THE AUTHOR.

Isolating Nebulosity An OSC camera incorporates individual colour filters over every pixel, commonly known as a Bayer filter. This filter array divides the pixels of your camera into three colours, much like a television screen: 50% of the pixels have green filters, 25% have blue, and the other 25% are red. When this array records a photo, software interpolates the gaps between the pixels in a single colour channel to create the full-colour image. In the past, the result was of perceptibly lower resolution than those made with monochrome images

The ﬁrst step to red luminance layering in ImagesPlus is to separate your image into its individual colour channels. Once accomplished, the program helpfully displays each channel in its assigned colour, as shown here.

recorded through colour filters. Interpolation algorithms have improved to the point that today the difference is almost imperceptible. Roughly a decade ago, noted astrophotographer Robert Gendler proposed that, much like combining narrowband hydrogen-alpha (Hα) images with colour data, a red-filtered image mixed with the luminosity information in an astrophoto will produce a “poor man’s” Hα-enhanced image. After all, Hα is captured in redfiltered images recorded with OSC and modified DSLRs. This technique turns out to be quite useful for OSC cameras. For example, in an average colour image of the Crab Nebula (M1), the red tendrils of gas are muted and difficult to

see. With an Hα exposure added to the photo, these tendrils become much more pronounced and vividly coloured. We can obtain a similar result by using a red luminance image, since the detail we wish to enhance is already recorded in the red channel. Instead of taking additional exposures through an Hα filter, we can record more colour exposures, combine them into a single new RGB image, and extract the red channel for use as a luminance image. Since you will only be using the red data, try to take almost twice as much exposure time for this red luminance as you did for the original unenhanced colour result to ensure a deep, smooth result. Most emission nebulae contain large amounts of Hα light. But they also contain smaller amounts of hydrogenbeta (Hβ), which emits in the blue/green spectral region, and hydrogen-gamma (Hγ), which emits in blue. If we tried to simply layer the red luminance onto the original colour image, the nebula would appear an odd salmon colour, skewed because we left out the data from Hβ and Hγ. Fortunately, imagers have devised a fix.

Luminance Layering in ImagesPlus We can produce a more natural colour balance by blending our red image with each of the remaining colour channels of our new RGB image in varying

percentages of intensity. At that point, we can then add the red luminance layer to bring out more detail. In order to make these combinations possible, it’s first necessary to calibrate, align, and combine all the images we’ll be using. Once done with that, split the colour channels of the new RGB image using the Colour / Split Colours function. A new window opens, where you can choose from a number of colour models to work with; select the RGB option. In a moment, you’ll have each colour channel displayed as a new image, along with the colour result. The individual channels are also displayed in their respective colours. At this point, we need to make a copy of the red channel by clicking on the red image and selecting View / Duplicate Image to Scale. Next, change one of the red images to greyscale by choosing Colour / Interpret & Mix Colours. Another dialogue window opens, where you’ll click the Grey button in the section Interpret Single Channel Image As. Click Apply, and then close the green and blue channel images. Now save and close the original red channel image; you will need this later. It’s important at this point to save this new “red luminance” image. Then you can stretch it to bring up the nebulosity you want to enhance in your final color result. Stretching an image in ImagesPlus is best done using the Micro Curves tool (Stretch / Micro Curves). You set the greyscale range that you’d like to boost using the two sliders, and you manipulate the curve using the two red points on the graph.

Extended nebulosity is contained in all of your images taken with OSC and modiﬁed DSLR cameras. But mixing a red luminosity channel requires a little more work to enhance your image while still retaining a pleasing colour balance. The Crab Nebula (M1) image at left is a normally processed OSC colour photo, while the centre image replaces the luminosity channel with the red channel data, distorting the overall colour in the photo. By mixing a small percentage of the red channel with the blue and green, a pleasing result is achieved at right.

www.skyandtelescope.com.au 83

Astrophotography Top: It’s difficult to see the entire range of values in the red channel when it’s displayed in its red colour in ImagesPlus, so the channel needs to be “reinterpeted” as a greyscale image. Bottom: Additional stretching to enhance the fainter nebulosity is easiest using the Micro Curves tool, whereas sharpening is best accomplished in ImagesPlus with the various sliders within the Multiresolution Sharpening Tool. Both can be used simultaneously on an image to give you greater control over the ﬁnal result.

You can sharpen exposures in ImagesPlus with The Multiresolution Sharpening Tool (Smooth Sharpen / Multiresolution Smooth / Sharpen…). This tool has many options for sharpening large and small details, controlling background brightness, and feathering your sharpening area. I prefer to concentrate on sharpening brighter parts of my image while avoiding the

dark background regions. The brighter areas in your red luminance image will translate into more vivid colours in your final result. Once you’re satisfied with your adjustments, save the processed red luminance image.

Recombining Channels Before combining the images, you’ll need to open the unenhanced red image

and make two additional copies of it. Use these three copies to simulate the Hβ and Hγ in each of the colour channels of the original result to retain a natural colour balance when the red luminance is applied. To do this, you’ll need to reinterpret each copy of the red channel to the respective colour it will modify. Select Colour / Interpret – Mix Colour, and change one of the copies to blue, the second to green. Next, using Special Functions / Combine Images Using / Blend Mode, Opacity, and Masks, you can start to build your new enhanced image by placing the original RGB image on the bottom of the image tree in normal mode, opacity 100%, and the processed greyscale luminance above it. Simply click OK in the Combine Images Setup window, and in a few moments, your list of open images will appear in the Combine Images dialogue window. ImagesPlus combines image layers from the bottom up, so ordering your images here is important to the final result. Click on the RGB image in the list and at the bottom left, select the Bottom button. This moves the image to the bottom layer. Make sure your red luminance file is on top and the three faux colour channels are in the middle. Your image will appear as greyscale at this point because we have to change the blending mode on each layer. The

Left: To ensure a pleasing colour balance in your ﬁnal result, you’ll want to blend a slight amount of the unenhanced red channel with the green and blue channels by opening the unenhanced red image, making two copies, and then reinterpeting one as green and the other as blue. Right: All your images are combined as layers in the Combine Images window from bottom to top, so make sure your colour photo is at the bottom, the unenhanced red channel copies are in the middle, and your red luminance is at the top of the stack.

84 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

unenhanced original RGB image at the bottom will remain the same, with its blending mode set to Normal with 100% opacity. To change the level that each enhanced red will contribute to each colour, select Overlay for the red, green, and blue layers. Next, adjust the Opacity slider for each of these enhancement channels — I use 60% for the red, 20% for the green, and 27% for the blue, though you can adjust these until you’re pleased with the final blend. Finally, select the red luminance layer and change the Blend Mode to luminosity. Watch as the results finally

Most nebula images can be enhanced using the red luminance layering technique. The author enhanced this deep photo of the Cone Nebula to bring out the subtle nebulosity in the very corners of the frame.

come together. The detail contained in the luminance layer translates to each of the layers beneath it. This is the key to getting the stretched and sharpened appearance into the final combined image. You can lower the opacity level of the red luminance to blend the layers to your liking. Once you’re pleased with the result, you’ll need to click the Flatten button at the bottom right to complete the action. Now you can boost the colour saturation or brightness if necessary before saving the final result. Comparing this to the original image

shows remarkable improvement with more colourful detail, all from the same source data. Whether you already take astrophotos or are the new owner of a DSLR or OSC camera dreaming about astronomical vistas, red luminance layering is a technique that can expand the use of your camera and help produce stunning results just by using data already available in your colour images.Ø Edward Henry images the night sky from his private observatory in rural northwest Wisconsin. www.skyandtelescope.com.au 85

Observing Projects

Why do I Observe Lunar Occultations? T

he first rather trite answer to this question is that I can always find the Moon in the sky! This sounds quite silly, but we of the older generation who started observing before the advent of ‘Go To’ telescopes remember spending considerable time carefully star hopping or poring over finder charts. My second point is that there is an imperative to observe. The event occurs at a particular time and if you are not there to record it, you won’t see it. This encourages motivation and a timely exit outside to observe! The main purpose in observing is to monitor the precise movement of the Moon as it is subjected to various influences and perturbations in our solar system. Careful analysis of the passage of this distant ‘occulting disc’ can also provide significant information about objects that are not simple ‘point’ sources. Predictions are obtained using Australian David Herald’s excellent Occult software, freely available on the web. Every month the Moon sweeps a ½o-wide swath around the sky, occulting stars as it goes. Its orbit is inclined 5.1o to the ecliptic (otherwise we would have a solar and lunar eclipse every month), and in the course of its 18.6-year cycle, the Moon occults objects in a band 11o wide centred on the ecliptic. Occultations are generally much easier to observe than reappearances. When the Moon is waxing and is conveniently visible in the evening sky, the unlit hemisphere leads and it is generally a simple matter to watch the Moon creep up to the star and occult it. From crescent phase until a little after First Quarter, light from the Earth faintly illuminates this hemisphere (the ‘Earthshine’), and the outline of the approaching lunar limb is clearly visible. The event then becomes a fairly easy countdown.

PETER ANDERSON

The author stands next to his 16-inch (41-cm) telescope in his home observatory. PETER ANDERSON

86 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

As Full Moon approaches, it becomes more difficult to follow stars to the instant of occultation, being lost in the glare of the advancing Moon. (The larger the telescope and the cleaner the optics, the better.) Only occultations of the brightest stars may be observed on the bright limb after Full Moon or reappearances on the bright limb before full. Reappearances are more difficult and are observed on the waning Moon after Full Moon. This generally means observing in late evening or early morning. Exact determination of the position of reappearance is assisted by the unlit hemisphere again becoming visible as Last Quarter approaches. Since the mid 1970s I have timed over 8,000 events from the same site. Some nights are busier than others. One memorable night the Moon transited the Pleiades and I timed 43 events. Over the years I have made many unusual observations. The most common of these are stepped disappearances and fast fades, generally

a close double star with each component being occulted quickly in turn. Any occultation longer than 1/10 second can easily be detected as noninstantaneous. (Test your ability to detect and time such short periods by listening to your DSLR camera shutter at 1/30, 1/15, 1/8, 1/4, and 1/2 second.) Other fading occultations may occur near the lunar polar regions as the star slides under the lunar limb at a shallow angle. Quick fades may also be caused by degradation of the image by an unstable atmosphere, particularly through the greater depth of atmosphere at low altitude. The cause is quite obvious because of the prior instability or nature of the star image. The usually invisible fainter companions of double stars are interesting. If the primary is occulted first, the secondary suddenly becomes visible, perhaps for several seconds. A faint companion emerging ahead of its primary can be spectacular and a great example is 1st magnitude Antares in

If the timing is right, an eclipsed Moon helps in observing lunar occultations. PETER ANDERSON

Scorpius. Antares is a huge, red supergiant, M-type star with a companion, 4½ magnitudes fainter, 3 arcseconds west. Because of the glare and proximity of Antares, this companion is very difficult to see. Antares’s apparent diameter is just over 0.04 arcsecond and so an occultation can easily take around 1/8 second. Thus visually an occultation or reappearance will certainly not seem instantaneous like other stars. For a reappearance, a brightish blue star appears followed seconds later by a brilliant orange flare like a struck match as Antares appears and disengages from the lunar limb. Observing a grazing lunar occultation is a great team activity. Observers spread out straddling the graze track. Their observations can supply very accurate lunar profiles of the lunar polar regions where these grazes occur. Small portable telescopes only directly resolve detail down to several kilometres on the lunar surface, but during a graze, resolution is limited merely by telescope spacing. One bright grazing occultation passed right over my observatory yielding 25 distinct events — dips in brightness, rapid increases, fading disappearances, ordinary disappearances, flashes, and reappearances. A lunar eclipse gives the rare opportunity to time quite faint

occultations at Full Moon, though the unusual lighting can be quite disorienting. On rare occasions the Moon will occult other objects, including planets. The first quasar discovered, 3C273, was pinpointed optically in 1963 as a result of an occultation of the radio source by the Moon. An observer will sometimes record a star absent from the predictions (and sometimes too the reverse happens, when a star that should be visible is too difficult to be seen!) Once recorded with a time, brightness, and position on the lunar limb, these ‘unidentifieds’ are easily chased up. Even with today’s very accurate predictions, a lunar occultation is still exciting to observe. The tension builds up as the seconds to predicted occultation tick off and the star disappears instantly as the airless surface of the Moon occults it. Occasionally the events may be a little early or late, indicating that the Moon is not quite in the calculated position. The recent development of video techniques using low-light security cameras and integrated GPS time systems produces a tenfold increase in accuracy over visual methods, and a permanent record. This points the way to the future.

The moment of truth arrives when you ‘reduce’ your observations prior to reporting them. These observations are processed on your own computer and the results are displayed immediately for checking. The Occult program even helps finding the pesky ‘unidentifieds’. Reports are swiftly dispatched by email, channelled via David Gault and the RASNZ Occultation Section, the coordinator for all occultations in this region. So lunar occultation observing is not routine and boring. As Forrest Gump could have observed, occultations are like a box of chocolates — you never know quite what you will get. When we are at home and are lucky enough to avoid the wet weather that "seems" to follow the Moon for a few days after New Moon and before each First Quarter, you will find me consulting my predictions and planning the next ten days of occultation disappearances. My wife is resigned to the fact that dinner time may need to be adjusted and that I couldn’t possibly go out somewhere tomorrow night ... the universe calls! ✦ A past president of the Astronomical Association of Queensland, Peter Anderson enjoys lecturing on cruise ships when he’s not observing occultations. www.skyandtelescope.com.au 87

Telescope Making

88 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

A 70-inch Amateur Telescope This monster Dob is likely the largest transportable amateur scope in the world.

hile most, if not all, amateur telescope makers get a touch of aperture fever now and then, only a handful have ever been as badly afflicted as Mike Clements. A 51-year-old longhaul truck driver from West Jordan, Utah, Mike has been fascinated with the night sky since his childhood in California. As an adult he built a 40inch (1-metre) Dobsonian with the help of friends. It earned him the nickname One Metre Mike. But even that impressive instrument eventually proved too small, so he set his sights on a larger telescope. In 2005 his friend Vaughn Parsons, a professional optics manufacturer, purchased an unaluminised, fully figured 70-inch (1.8-metre) mirror at a surplus auction. It was originally fabricated for a Cold War-era spy satellite, but a minor edge chip doomed it to storage and eventual sale. Parsons promptly called Mike, who had often spoken of wanting to build a telescope larger than 1 metre. “I couldn’t believe it,” Mike said when he heard the news. “I had to have it.” He purchased the mirror from Parsons without knowing its exact optical figure. “I wasn’t sure if it was intended to be part of some complex optical

Left: Utah telescope maker Mike Clements is dwarfed by his 70-inch f/6.1 monster Dobsonian. The telescope is likely the largest transportable amateur instrument in the world. Right: Mike Clements stands at the eyepiece of his 70-inch reﬂector. Thanks to a ﬂat secondary mirror that folds the instrument’s 11-metre light path, the eyepiece is never more than about 4 metres off the ground. All photos by the author.

system. None of us knew if it would even work in a visual telescope.” At least the edge chip that kept the mirror from going into space didn’t extend onto the optical surface. And though the mirror blank was a “lightweight” honeycomb structure, it still weighed in at about 400 kilograms. Although a few people tried to dissuade Mike from tackling such a big project, he forged ahead with his bigscope dream. “He built a model out of Popsicle sticks,” recalls Steve Dodds, owner of Nova Optical Systems and Mike’s friend and mentor on the project. “I bought him a computeraided design program, but he never touched it.” Instead the telescope came into being one sub-assembly at a time — from Mike’s imagination, directly to steel. He even taught himself to weld while building the scope. At f/6.1, the primary mirror has a focal length of almost 11 metres. So Mike used a 29-inch (74-cm), round secondary mirror to fold the light path back on itself at a slight angle, enabling him to have the focuser at the side of the telescope’s “tube” only about 4 metres off the ground when the 11-metre-long telescope points overhead. He used a regular 2-inch star diagonal as a tertiary mirror to place the eyepiece at a nearly horizontal angle, like a conventional Dobsonian. The finished telescope is about the size of a bus, but for viewing a large part of the sky, only a few steps up a ladder are needed to reach the eyepiece. “Every spare dime he made went into it,” says Dodds, who volunteered one of Nova Optical’s buildings as a workshop for the project when Mike started

BRUCE LIEBERMAN

fabricating the scope in late 2011. Only when a structure to hold the primary was completed could the mirror’s figure be evaluated. The testing was done outside since the focal length of the primary prevented indoor testing. “Steve was testing it with a Ronchi screen at the radius of curvature,” Mike says, “so he had to be nearly 20 metres away from the mirror. I was nervous and holding my breath waiting to hear what Steve was going to say after looking at the mirror!” Nevertheless,

www.skyandtelescope.com.au 89

Telescope Making Mike’s jitters were relieved when Dodds announced that the mirror was a good paraboloid, showing just a little overcorrection, but well within acceptable limits. Almost as daunting as building the telescope was the prospect of aluminising the primary and secondary mirrors. “We got a bid of $7,000 for just the primary from an out-of-state company,” says Mike, “and there was no guarantee that the mirror wouldn’t be damaged in the process.” A solution was found in the form of a spray-on silvering process that professional opticians use when they need to quickly test a mirror. Applying the coating requires a weed sprayer or automotive paint gun. “I had to practice a bit,” says Mike, “since it takes a while to get the method down, and I botched my first attempt.” But eventually he successfully silvered the primary and secondary mirrors. Dodds thinks that with some protection, the mirrors will only need recoating once or twice a year. The coating is inexpensive and about 5% more reflective than standard

aluminising. Furthermore, Dodds’s tests revealed that the mirror’s figure was not compromised by the sprayon coating. First light for the 1,400-kilogram telescope came on a cool evening in mid-2013. Mike’s target was M57, the famed Ring Nebula in Lyra. Usually a small object in most amateur telescopes, the ring filled much of the eyepiece field of view. The seeing wasn’t ideal that night, but on better nights the central star was easily visible. The telescope worked — and it worked well. The behemoth has a usable magnification range from a low of

Almost as daunting as building the telescope was the prospect of aluminishing the primary and secondary mirrors.

The scope’s 70-inch mirror is supported on a 9-point cell, a conﬁguration adequate for a cellular mirror that is nearly 30 cm thick. The short, white tubes on the left side of the mirror box are sight tubes for rough aiming of the scope.

90 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

The instrument’s ﬁnder and focuser are mounted at the side of the scope where a 2-inch star diagonal places the eyepiece horizontal for comfortable viewing. A length of tubing ahead of the focuser prevents stray light from reaching the focal plane.

about 280× (limited by the shadow of the secondary mirror visible in the exit pupil) to as high as the seeing will allow. Typically, 400× is the maximum useful power, but on rare nights Mike can push it higher. The telescope is regularly used by Mike, his friends, and members of the Salt Lake Astronomical Society, but there are still some tweaks to be made. Mike is adding motor drives for automated tracking, and he plans to buy a trailer so that he can transport the monster Dob to National Parks and star parties. He hopes to have all this ready in time for the May 2014 RTMC Astronomy Expo, held near Big Bear Lake in Southern California. “I want to take it all around the country and let as many people as possible look through it,” says Mike. “That’s always been a high priority for me — I want to share it.” Although some contend that the 70inch is not the largest amateur-made telescope (citing the 72-inch at Ireland’s Birr Castle made by Lord Rosse in the mid-19th century), Mike’s is certainly the largest transportable amateur-made scope. At least for now. Knowing Mike’s passion for showing people the sky, and his determination to finish big projects, I would not be surprised if one day we might have to call him “Hundred Inch Mike!” ✦ Chuck Hards is an avid amateur telescope maker and member of the Salt Lake Astronomical Society. He can be contacted at chuck.hards@gmail.com.

Gallery

Astrophotos from our readers

▴MOONRISE OVER BRISBANE Stephen Mudge

The Full Moon rises over Brisbane in this image taken on the evening of 16 February, 2014 with a Canon 50D camera and 70-200mm telephoto lens at 200mm.

◀SUNSPOT AR1944 David Hough

One of the biggest sunspots of this solar cycle, AR1944 (far right of the Sun) rotates out of view. This mosaic of the Sun was taken with a DMK41 camera on 12 January, 2014 and processed in Photoshop.

www.skyandtelescope.com.au 91

Gallery

◀STELLAR FACTORY Steve Mazlin and Jack Harvey

This colourful moiac image, taken with a RCOS 16-inch (41-cm) Ritchey-Chretien reﬂector and Apogee U9 CCD camera, captures the giant star-forming region NGC 2070 in the Large Magellanic Cloud.

▾COSMIC BUBBLE Marco Lorenzi

This bubble-shaped nebula, catalogued as Sharpless 2-308, lies 5,200 light-years in Canis Major. At its heart is a Wolf-Rayet star (bright blue star below) whose powerful winds are shaping the nebula. This image was taken with a TEC 140-mm APO ED refractor and FLI Proline 16803 camera.

HOW TO SUBMIT YOUR IMAGES Images should be sent electronically. Please first send a low-res JPG version to contributions@skyandtelescope.com.au, and we’ll get back to you with information on how to send your hi-res versions if selected. Please provide full details of all images, eg. date and time taken; telescope and/or lens used; mount; imaging equipment type and model; film (if used); filter (if used); exposure or integration time; and any software processing employed. Readers who have a contributed image published in Australian Sky & Telescope will receive a 3-issue subscription to the magazine.

92 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

▴COMETARY GLOBULES Rolf Olsen

Within these dense dark clouds in Puppis, new stars are being born. One, in the far right globule, is starting to show. This image was taken with a QSI 683wsg camera and homebuilt 12.5-inch (32-cm) reﬂector.

▶SOUTHERN JOURNEY Carlos Orue

Taken with a Canon 5D camera, this nightscape of the southern sky was taken from the Riverina, New South Wales. www.skyandtelescope.com.au 93

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Focal Point Nick Howes

How the Web Saved the Webb A group of enthusiasts helped rescue an $8 billion treasure.

t the U.S. Northeast Astronomy Forum in 2011, I listened to astronomer Heidi Hammel enthusiastically describe the wonders of the James Webb Space Telescope. Toward the end of her talk, she put out a plea for the audience to write to their U.S. Congressional representatives because there was a very real possibility that telescope funding could be cut. The political forces in Congress, even before the current sequestration, had found the JWST program’s budget overruns and mismanagement a little too much to swallow. In July 2011, with budget cuts looming at NASA, a House committee recommended culling the so-called “successor to Hubble.” The James Webb Space Telescope — named after NASA’s second administrator, a seminal leader who was not averse to fighting for ambitious endeavours in science and technology — was already US$3.5 billion into development. Moreover, this is an international project, and a European instrument was at the testing stage. Comparisons of JWST’s plight to that of the fight to save Hubble rippled across the internet. Everyone from science buffs to the engineers building JWST were reminding people that Hubble had been the most successful science instrument in history, and that it was unthinkable to scrap NASA’s next great space observatory. It was time to act. The campaign kicked off with Twitter. Hashtags relating to the scope permeated the social network, encouraging others to read the news that Congress might scrap NASA’s ultimate eye on the universe. Raphael Perrino, who had previous experience with saving science projects, picked up the tweets, and after a brief e-mail exchange, he and a small team of enthusiasts set up a “Save the Webb” Facebook page, which went viral, rapidly attracting thousands of passionate followers. 98 AUSTRALIAN SKY & TELESCOPE MAY/JUNE 2014

NASA / MSFC / DAVID HIGGINBOTHAM / EMMETT GIVEN

... it was unthinkable to scrap NASA's next great space observatory. Concurrently, Kyle Sullivan and Blair Schumacher launched an online petition, and within days, joined efforts with me and Raphael. Over the next few weeks, a group of 10 science advocates, web and graphic designers, bloggers, and outreach specialists did everything from lobbying Congress to designing bumper stickers. We all played a major role in getting the message out: this telescope had to be saved. U.S. team members encouraged everyone to sign petitions, write to their Congressmen, and spread the word. Video competitions saw some epic film entries, indicative of the level of passion people felt to save the scope. After four months of rallying support for JWST, supporters breathed a collective sigh of relief when news came that Congress had agreed to fund the scope for launch later this

decade. But had the team really made a difference? The small core group of people, spread over two continents and multiple states, had never even met in person. All had regular day jobs, but we all put our heart and soul into the campaign. Then the letters arrived, from Congressmen, lobbyists, policy analysts, scientists, and Capitol Hill staffers, expressing their sincere gratitude for our efforts and saying how our team’s passion had made a difference. So when people voice skepticism about “social not-working” websites, think of what they can do, when, toward the end of this decade, if everything goes well, the most astonishing images and scientific discoveries of our age are beamed back to us from a tennis-court-sized infrared telescope, which a small group of social media space activists helped rescue from the brink. ✦ Nick Howes is a freelance science writer and Pro-Am Program Manager for the Faulkes Telescope Project, which operates two 2-metre telescopes at Siding Spring Observatory and in Hawaii.

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