Astronomical Calendar 2011

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Astronomical Calendar 2011

Watery Constellations

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Cover picture: The watery constellations fill a quarter of the sky. Well, the only body of water is the river Eridanus, but there must be a sea for Cetus the whale, Delphinus the dolphin, Pisces the two fishes, Piscis Austrinus the southern fish, Dorado the goldfish, and Hydrus the (small male) water monster to swim in.

Volans is a f lying fish, and I suppose that Grus the crane, Phoenix the firebird, and Tucana the toucan are also f lying over. In far separate parts of the sky are Hydra the female water-monster, largest of present constellations, and the still larger ancient constellation Argo the ship, now divided into Carina the keel, Puppis the poop, and Vela the sails, to which we can add Pyxis the ship’s compass. All these amount to about a fifth of the celestial sphere (see the list of areas in the Astronomical Companion’s section on constellations). But there is more: half of Aquarius the water-carrier consists of the water he is pouring (why?) from his jar; Capricornus is half goat and half fish; and Taurus the bull and Pegasus the winged horse must have their rear halves hidden underwater, since the constellation figures show only their front halves; so if we add half of those the total comes to about a quarter. Andromeda is chained to a coastal rock, waiting to be devoured by Cetus; we need not count her, nor her rescuer Perseus and her parents Cassiopeia and Cepheus, but they must be looking out over the sea, along with Lacerta the lizard and Cygnus the swan. Fornax and Sculptor seem to be on an industrial south-seas island (they are among the constellations invented in the 18th century, their full names being Fornax Chemica the chemical furnace and Apparatus Sculptoris the sculptor’s workshop). The whole dark bowl centered on Pisces and surrounded by the arc of the northern Milky Way is the sky’s Ocean. Its only first-magnitude stars are Fomalhaut the mouth of the southern fish and Achernar the mouth of the river.

I had sometimes felt, looking at the constellation figures in the old atlases— the heroes and bears adrift as if in zero gravity—that there ought to be ways of drawing them so that they fill their spaces, fitting together like the doves and fishes in an Escher tiling. A long time ago I set about making a picture of the watery constellations. Then I realized that a picture of such a large area would have to be a picture of the inside of a spherical surface. I plotted the constellation boundaries of a whole hemisphere, centered on the equinox point in Pisces (a hemisphere at right angles to the two in the central opening of this book, and oriented with the ecliptic level). I plotted the constellation names at two distances, the radius of the sphere and a bit beyond, to help me with the solidity.

I had to print the eighteen-inch-wide picture on two sheets of paper, and I cut it to a circle and stuck it on a large piece of russet-red cardboard. The picture did look like a solid hemisphere, the inside of half of a coconut. I started painting the constellation images over it, but there were many difficulties. Painting hid the stars and boundaries that were to be the guides. (The stars should have become glints of light on the figures; or perhaps my idea was that in the end I should prick through the stars.) But that was the least of it. Not just the Wateries would have to be painted, but half of all the constellations. What is the scale, when a whale stretches alongside a river? (There is a star that helps to trace the upper course of Eridanus but is called Pi Ceti because it is also in the whale’s chest!) There is no scale in the surreal society of the constellations; scale has to be abandoned. The figures could be painted as on the bowl, becoming foreshortened toward the rim; or they could be solid, casting their own shadows—Orion on the left and Sagittarius on the right bulging from the surface like statuary seen in profile, so that the whole thing would get to look like a bowlful of sculpture, with the light correct on all its surfaces—a task for a Tiepolo.

This ideal picture will have to exist in the mind. I let the picture lie and decay.

But I revive it because I like my little Lizard (the zigzag constellation Lacerta, not even a constellation of the Water, but one of the spectators on very dry land nearby).

Water covers a quarter of the sky, but seventy percent of our planet. No other planet shows this division of its surface into land and water, a particolored pattern with a third and mobile layer, the clouds, which are uplifted water. We have the luck to have another planet near us, the Moon, and we are impressed by it and can almost read by its light. But a man on the Moon sees a neighbor planet that is nearly four times as wide, and a hundred times as bright; he can certainly read by its light. Instead of being the dull gray of dust (which the Moon’s surface actually is) the larger planet is brilliant blue and white, with f lakes of brown and green under the white. And since it has atmosphere and the Moon does not, the full Moon seen from Earth seems to give off a pale glare that drowns the stars; but the sky in which the full Earth f loats is blacker and richer in stars—all of them clear and steady—than any we see from a desert peak. And around the full Earth wraps an exquisitely thin ring of blue-white. When the Earth is “new”—eclipsing the Sun—this ring turns to fiery orange.

Unfortunately Earth’s film of water and air, in which we live, is souring. The world ocean is becoming acidic, at a rate exactly in step with the increase of carbon dioxide in the air. The air is heating, at a rate governed by the same increase of that gas, though more irregularly, because of lesser factors such as volcanoes and jet streams. The increase of carbon dioxide in the atmosphere is caused, like the rapid global extinction of species, by the increase of humans and their consumption.

The Drake equation is a formula for estimating how much life there is in the universe, at any rate in our own Milky Way galaxy, life with which we might communicate. Frank Drake of the National Radio Astronomy Observatory at Green Bank in West Virginia made in 1960 the first search for artificial radio signals from space. In November 1961 eleven scientists, calling themselves the Order of the Dolphin, met at Green Bank to discuss this new field—SETI, the search for extra-terrestrial intelligence—and Drake jotted a list of topics for the agenda, then realized that they formed an equation:

N = R* × fp × ne × fl × fi × fc × L This means: The likely present number of such civilizations is the yearly rate at which stars are born in the galaxy, multiplied by the fraction of those that have planets, multiplied by the average number of planets in a planetary system that have life-possible conditions, multiplied by the fraction of those on which life does develop, multiplied by the fraction of those where the life reaches intelligence, multiplied by the fraction of those where it reaches a technological level at which it can and is willing to communicate across space, multiplied by the average lifetime in years of such civilizations.

R*, stars coming into existence in the galaxy per year. This is about the only one of these terms that can be narrowed down with some confidence, by astrophysical science. Drake used 10, the estimate now is 7. fp, the fraction of those stars that have planets. Drake’s guess: half. In 1992 extra-solar planets started being discovered, and about 500 are already known; it is thought that at least 40% of Sun-like stars have planets. Some kinds of planet are much easier to discover than others; but some kinds of stars may not have them. We should perhaps bump this up to at least 0.6. ne, the average number of planets, in a planetary system, that have conditions allowing life to start. Drake said 2, since, in the only sample system we know, Mars probably had such conditions long ago. And some satellites may have conditions for kinds of life different from ours. This may be the most uncertain of all these uncertain terms. The variety of planets being discovered, the sheer luck of some of the factors allowing life to start on Earth, and the unsolved problem of how it did start, suggest to different scientists that the average of habitable places in a planetary system could be anywhere from several down to almost zero. I’m going to pick a still optimistic 0.5. fl, the fraction of those that do develop life. Drake guessed 1; all planets that can brew life, will. That still seems fairly likely, single-celled life having built itself on Earth in less than a billion years. fi, the fraction of life-bearing planets on which some of the life reaches intelligence. Drake guessed 0.01, a hundredth. This is another controversial term.

It could be 1 (all) or it could be tiny. On Earth, after four billion years, just one out of the billions of species that came and went became complex enough to use language. (Dolphin, octopus, and crow display intelligence, but not that kind.)

Other life-bearing lumps may allow only primitive life to cling to them. Let’s keep Drake’s blind guess. fc, the fraction of those where the intelligent life reaches a technological level at which it can, and wants to, communicate across space. Again Drake guessed 0.01. Our species appeared only 200,000 years ago, and began to send out radio signals a century ago. We may feel, with evidence as slender as for the other terms, that intelligent life will probably become technological, and that it should have little reason not to communicate if it can. Drake seems pessimistice here; let’s greatly raise his guess to 0.5.

L, the average duration, in years, of such high-tech civilizations. Drake guessed 10,000 years. In other words, our civilization will probably survive that long from essentially now. Let’s think about this later.

Multiplying Drake’s figures: 10 × 0.5 × 2 × 1 × 0.01 × 0.01 = 0.001, before considering the last term, the lifespan. Multiplying by 10,000 years gives 10.

Just ten places, out among the 200 billion stars across the 100,000 light-yearswide galaxy, where consciousness exists that could share consciousness with us.

Since 1961 Drake and others have varied their estimates so that the answer could be anywhere from 0.2 to 20,000,000,000.

Multiplying the figures I’ve adopted, except for the last: 7 × 0.6 × 0.5 × 1 × 0.01 × 0.5 = 0.0105, which is 10.5 times more optimistic than Drake. But what can we guess for L? If Drake was right about that, the big answer is 105. Let’s call it 100. Ten times as many such civilizations, yet the nearest of them could be 10,000 light-years away. Or of course, by a grossly lucky f luke such as science fiction is free to imagine, it could be just four and a half light-years away at Alpha Centauri. Then each message in our telephone conversation would get a reply in only nine years.

So which part of this actually matters? To know that conscious life exists elsewhere would be of supreme importance philosophically, and might have effects on our international behavior. But communication, with 10,000 years to wait for each answer, or even only nine, can that be worth anything? Perhaps so, to beings who live much more slowly than us, because vastly larger (I don’t know whether science fiction has made this suggestion). Looking at ants, I surmise that experience runs faster for them than for us, and that to them we appear stationary. As ants to us, so perhaps us to cloud-like beings for whom a century is a second.

I think the importance of L, the last term in the equation, is not so much in estimating N as in itself: the likely lifetime of advanced civilization. It now looks as if L could be as short as a century. In that case the number of communicating civilizations across the galaxy is 0.0105×100 = 1.05. Ours, and a small chance of just one other.

Perhaps we need another term that would help to estimate L: fw: the fraction of those societies having high technology that also have wisdom. Animals cannot have, or cannot pass on for long, the quality of foolishness; if foolish behavior predominates, the species dies out. But the species self-named Homo sapiens, wise man, is in danger of behaving foolishly.

See a chart of the sky’s Ocean on page 73. And exoplanets on page 55. And for my take on global heating, www.UniversalWorkshop.com/climate.htm.

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ASTRONOMICAL CALENDAR 2011 by Guy Ottewell

Sponsored by the Department of Physics, Furman University, Greenville, South Carolina

the Astronomical League 9201 Ward Parkway, Suite 100, Kansas City, MO 64114 816-DEEP-SKY www.astroleague.org

Universal Workshop www.universalworkshop.com

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Copyright © 2010 by Guy Ottewell. Printed in the United States of America. All rights reserved. Parts may be reproduced with prior permission and with acknowledgment.

The first issue of this annual book was for the year 1974.

ISBN 978-0-934546-59-1

Julian Date at 1.0 of month 2455562.5

ISSN 1051-6174 January

Where? What parts of the book are true for what parts of the Earth? MOST. But see the explanation on page 9.

2455593.5

About the contributing writers: Fred Schaaf is the author or co-author of thirteen books. His past books include Wonders of the Sky and The Starry Room (both available from Dover Publications), Mankind’s Comet (co-authored with Guy),, The 50 Best Sights in Astronomy and The Brightest Stars. Fred writes the stars and planets columns, and other features, in Sky & Telescope and is a Contributing Editor to the magazine. He has written the weekly “South Jersey Skies” column in the Atlantic City, New Jersey, newspaper for over 30 years. He has been a light-pollution activist for more than 25 years. He teaches at Rowan University in Glassboro, NJ. Fred wishes to acknowledge the calculations of Steve Albers for several of the events listed in “Observers’ Highlights.”

Clifford Cunningham, a graduate of the University of Waterloo, is a Canadian astronomer whose specialty is asteroids. He has written or edited 11 books, his first being Introduction to Asteroids (1988). In 1990, asteroid 4276 Clifford was named in his honour by the Minor Planet Center. His database, The Minor Planet Index to Scientific Papers, is used by NASA in its planetary data system. He is a contributing editor to Mercury magazine and is now working on his PhD in the history of astronomy. In 1999 he appeared as a Starf leet officer in an episode of “Star Trek: Deep Space Nine.”

Alastair McBeath is a British observational meteor astronomer. He was Vice-President of the International Meteor Organization (IMO) from 1989 to 2009, and remains Metor Section Director to the Society for Popular Astronomy (SPA). He still writes the annual “IMO Meteor Shower Calendar, and regular fortnightly meteor columns in the SPA Electronic News Bulletins. Among hundreds of published articles, papers, columns and letters on various astronomical topics in professional and amateur journals, magazines and periodic handbooks, he was co-editor and co-author of the IMO’s Handbook for Visual Meteor Observers in 1995, and has written several other books on astronomical observing and mythology. In 2003, he set up the Meteor Beliefs Project (www.imo.net/projects/beliefs) with his colleague Andrei Dorian Gheorghe, to collect and publish notes found in a range of sources, ref lecting past and current beliefs about meteors. He was part of the editorial team for the all-technique IMO Observing Handbook, published in late 2008.

Alan Hale earned his Ph.D. in astronomy from New Mexico State University in 1992, and is founder and director of the Earthrise Institute, an independent research and educational organization based in New Mexico. He has studied comets, near-Earth asteroids, and planetary systems around other stars. He is best known as co-discoverer of Comet Hale-Bopp, and has confirmed numerous comet discoveries and acted as a visual observations recorder for the International Halley Watch. He is the author of Everybody’s Comet: A Layman’s Guide to Comet Hale-Bopp (High-Lonesome Books, 1996), and several research papers and popular astronomical articles. He writes “In Our Skies,” a weekly newspaper column on astronomy and space. He is active in what he calls “science diplomacy,” having led two delegations of American scientists and students in visits to Iran, and is developing Earthrise, a project that will encourage students to form international collaborations for carrying out astronomical activities.

Joe Rao is a television meteorologist in New York’s Hudson Valley, appearing weeknights on News 12 Westchester. But he has also been an assiduous amateur astronomer for 40 years, with a particular interest in eclipses. He has co-led two eclipse expeditions and has served as on-board meteorologist for three eclipse cruises. He is a regular contributor to Sky & Telescope and Natural History magazines, as well as Space.com and The Farmers’ Almanac. He also writes a Sunday feature, “Sky Watch,” for The New York Times. Since 1986, he has been an instructor and guest lecturer at New York’s Hayden Planetarium.

Richard Nugent holds an M.S. in astronomy from the University of South Florida. He worked at NASA’s Lyndon B. Johnson Space Center in Houston, Texas, specializing in analysis of imagery from the LANDSAT satellites. He was also in the Space Shuttle program’s Guidance, Navigation and Control division performing critical real time calculations of orbits and rendezvous maneuvers including instrument pointing to celestial objects. He has over 60 publications in professional and amateur journals. He is the Executive Secretary of the International Occultation Timing Association (IOTA) and has traveled worldwide on over 120 scientific expeditions involving lunar and asteroid occultations and solar eclipses in IOTA’s long term study to measure possible solar radius variations. He is the author/editor of IOTA’s new book Chasing the Shadow: The IOTA Occultation Observer’s Manual.

February 2455621.5

March 2455652.5

April

2455682.5

May 2455713.5

June 2455743.5

July

2455774.5

August 2455805.5

September 2455835.5

October 2455866.5

November 2455896.5

December

Author’s Preface. I am responsible for all parts of the book other than those under contributors’ by-lines, including illustrations (except for maps drawn by Richard Nugent for his “Occultations” section) and captions.

For this year as for 2010, Joe Rao has contributed the articles on the planets Mercury to Saturn, following approximately the styles in which I had previously written them.

Sun Mon Tue Wed Thu

Fri

2 9 16 23 30 6 13 20 27 6 13 20 27 3 10 17 24 1 8 15 22 29 5 12 19 26 3 10 17 24 31 7 14 21 28 4 11 18 25 2 9 16 23 30 6 13 20 27 4 11 18 25 1

7 14 21 28 4 11 18 25 4 11 18 25 1 8 15 22 29 6 13 20 27 3 10 17 24 1 8 15 22 29 5 12 19 26 2 9 16 23 30 7 14 21 28 4 11 18 25 2 9 16 23 30

3 10 17 24 31 7 14 21 28 7 14 21 28 4 11 18 25 2 9 16 23 30 6 13 20 27 4 11 18 25 1 8 15 22 29 5 12 19 26 3 10 17 24 31 7 14 21 28 5 12 19 26

4 11 18 25 1 8 15 22 1 8 15 22 29 5 12 19 26 3 10 17 24 31 7 14 21 28 5 12 19 26 2 9 16 23 30 6 13 20 27 4 11 18 25 1 8 15 22 29 6 13 20 27

5 12 19 26 2 9 16 23 2 9 16 23 30 6 13 20 27 4 11 18 25 1 8 15 22 29 6 13 20 27 3 10 17 24 31 7 14 21 28 5 12 19 26 2 9 16 23 30 7 14 21 28

6 13 20 27 3 10 17 24 3 10 17 24 31 7 14 21 28 5 12 19 26 2 9 16 23 30 7 14 21 28 4 11 18 25 1 8 15 22 29 6 13 20 27 3 10 17 24 1 8 15 22 29

Astronomical Companion

$26.95

General guide to astronomy (not annual), with many 3-D diagrams

Albedo to Zodiac

Venus transit over Sun

$11.00 Glossary of astronomical names and terms, with pronunciation, origin, and meaning To Know the Stars $8.00 Children’s introduction to astronomy The Thousand-Yard Model, or, The Earth as a Peppercorn $6.00 Instructions for a walk making vivid the scale of the solar system The Under-Standing of Eclipses $14.00 The geometry, history, and beauty of eclipses Berenice’s Hair $18.00 Story of the stolen tress that became the constellation Coma Berenices The Troy Town Tale $29.00 The whole legend of Troy, in the form of a novel

Sat 1 8 15 22 29 5 12 19 26 5 12 19 26 2 9 16 23 30 7 14 21 28 4 11 18 25 2 9 16 23 30 6 13 20 27 3 10 17 24 1 8 15 22 29 5 12 19 26 3 10 17 24 31

Darker blue means less moonlight in the following night.

Portrait of a Million

Some other publications by Guy Ottewell:

Earthrise over Moon

2455927.5

2011

$7.00 Poster conveying the concept of a million, with selected million-facts American Indian Map, and Navajo Map . . . . . . . . . . . $8.00 The Arithmetic of Voting . . . . . . . . . . . $2.00 Language (poems) . . . . . . . . . . . $9.00 Pembrokeshire prints . . . . . . . . . . . $15.00 Plurry: a musical instrument . . . . . . . . . . . $6.00 The Spiral Library . . . . . . . . . . . $5.00 Stripe Latin: a grammar game . . . . . . . . . . . $7.00 Ten-Minute History of the World; and, Queen Guinevere’s Rules. . . . . . . . . . . $4.00 Think Like a Mother: a photo book of human rights . . . . . . . . . . . $8.00 Turkey, A Very Short History . . . . . . . . . . . $4.00 The Winged Velocipede; or, how to f ly overseas with your bicycle . . . . . . . . . . . $5.00 For descriptions of these and more, see www.universalworkshop.com

Universal Workshop P.O. Box 102, Raynham, MA 02767-0102, U.S.A. 800-533-5083 (toll-free) 508-802-5660 fax 508-967-2702 customerservice@UniversalWorkshop.com author: guy@universalworkshop.com

www.UniversalWorkshop.com

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Astronomical Calendar 2011

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1st.) In every span of 400 years after 1582 (beginning of the Gregorian calendar) the numbers of Sundays-the-13th, Mondays-the-13th etc. are: 687 685 685 687 684 688 684.

SUN. May Day or Beltane. See Ast. Companion, SEASONS. ° 14 SAT. (10 UT= 6 EDT) Moon 7.6° S.S.W. of Saturn (about 137° from Sun in evening ( 0 UT=20 edt) Moon 7.3° N.N.W. of Mercury (25° from Sun in morning sky). sky). ( 3 UT=23 edt) Mars 0.36° N.N.W. of Jupiter (18° from Sun in morning sky); (11 UT= 7 EDT) The equation of time reaches a shallow maximum of 3.66 minmagnitudes 1.2 and —2.1. Conjunction in r.a. is 8 hours later. utes. See Feb. 11.

(16 UT=12 EDT) Moon 5.6° N.N.W. of Jupiter (about 18° from Sun in morning (12 UT= 8 EDT) í “ Sun enters Taurus, at longitude 53.34° on the ecliptic. sky). ______________________________________________________________________ (17 UT=13 EDT) Moon 5.3° N.N.W. of Mars (18° from Sun in morning sky).

15 SUN. ( 5 UT= 1 EDT) Moon 2.7° S.W. of Spica (about 149° from Sun in evening sky).

Tue. ( 6:50 UT= 2:50 EDT) í ’ Moon new. Beginning of lunation 1093.

(11 UT= 7 EDT) Moon at perigee. Distance 56.78 earth-radii.

Wed. (19 UT=15 EDT) Moon 2.2° S.S.E. of Pleiades (17° from Sun in evening sky).

(13 UT= 9 EDT) C/2010 G2 Hill only 1.4° from the north celestial pole. See Thu. (14 UT=10 EDT) Moon 6.7° N. of Aldebaran (26° from Sun in evening sky).

COMETS. Fri. Eta Aquarid meteors. See METEORS. Very favorable year for this major shower.

16 Mon. May Arietid meteors (radio shower). See METEORS. (14:57 UT=10:57 EDT) Moon at descending node (longitude 83.8°).

17 Tue. (11:07 UT= 7:07 EDT) í ” Moon full. See SPECIAL MOONS. SAT. Astronomy Day; started in 1973, and held in April or May on the Saturday clos18 Wed. ( 7 UT= 3 EDT) Mercury 1.4° S.E. of Venus (24° from Sun in morning sky); est to the first-quarter Moon. For information: www.astroleague.org, and Gary magnitudes 0.0 and —3.9. A second appulse and conjunction in longitude without Tomlinson, Astronomy Day Headquarters, 30 Stargazer Lane, Comstock Park, Mich. conjunction in r.a.; see May 8.

49321 (gtomlins@sbcglobal.net; 616-784-9518). And now there will also be a Fall ( 8 UT= 4 EDT) Moon 3.4° N. of Antares (about 167° from Sun in morning sky).

Astronomy Day on Oct. 1. ° 19 Thu. ( 2 UT=22 edt) Mars at heliocentric conjunction with Jupiter; that is, passes it as (19 UT=15 EDT) Mercury at greatest elongation west, 26.6° from the Sun. seen from the Sun. Their heliocentric longitude is 20.4°. _____________________________________________________weeks____________ ( 9:04 UT= 5:04 EDT) Moon at ascending node (longitude 263.5°).

SUN. ( 5 UT= 1 EDT) Mercury 1.4° S.S.E. of Venus (27° from Sun in morning sky); (14 UT=10 EDT) Mercury at greatest latitude south of the ecliptic plane (—7.0°). magnitudes 0.5 and —3.9. Appulse and (34 hours later) conjunction in longitude, but ° 20 Fri. Omicron Cetid meteors (radio shower). See METEORS. none in r.a. See May 18. ( 8 UT= 4 EDT) Moon 3.4° S. of Pluto (142° from Sun in morning sky).

(21 UT=17 EDT) Moon 9.2° S.S.W. of Pollux (about 65° from Sun in evening sky). zenith zenith ° 21 SAT. ( 8 UT= 4 EDT) Mercury 2.1° S.S.E. of Mars (22° from Sun in morning sky); Mon. Eta Lyrid meteors. See METEORS. magnitudes —0.2 and 1.3. Conjunction in r.a. is 31 hours earlier.

Epsilon Arietid meteors (radio shower). See METEORS. ( 8 UT= 4 EDT) Mercury, Venus, and Mars within circle of diameter 2.13°; 23° (23 UT=19 EDT) Moon 4.9° S.S.W. of Beehive Cluster (about 78° from Sun in west of the Sun. evening sky). ( 9 UT= 5 EDT) Sun enters the astrological sign Gemini, i.e. its longitude is 60°.

Tue. ( 9 UT= 5 EDT) Mars and Saturn at heliocentric opposition; that is, they are on o 80 o 80 o But astronomically it is still in Taurus. See Ast. Companion, PRECESSION. opposite sides of the Sun. Their heliocentric longitudes are 15.1° and 195.1°. 8 0 y a ______________________________________________________________________ W (20:32 UT=16:32 EDT) í ‘ Moon at first quarter. y ° 22 SUN. ( 7 UT= 3 EDT) Neptune at west quadrature.

Wed. ( 4 UT=24 edt) Venus at greatest latitude k south of the ecliptic plane (—3.4°).

Mi l UT= 5k EDT) Venus 0.99° S.S.E. of Mars (23° from Sun in morning sky); mag(14 UT=10 EDT) Moon 5.2° S.S.W. of Regulus (about 99° from Sun in evening ¹ 23 Mon. ( 9 l y i nitudes —3.9 and 1.3. Conjunction in r.a. is 18 hours earlier. sky).

M Wof Neptune (92° from Sun in morning sky). Âą 24 Tue. (15 UT=11 EDT) Moon 5.4° N.N.W. (16 UT=12 EDT) Venus 0.57° S.S.E. of Jupiter (26° from Sun in morning 7sky); 70 o 70 o 0o a (18:51 UT=14:51 EDT) í ? Moon at last quarter. magnitudes —3.9 and —2.1. Conjunction in r.a. is 6 hours earlier. y (17 UT=13 EDT) Venus, Mars, and Jupiter within circle of diameter 5.54°; 24° Âą 27 Fri. ( 7 UT= 3 EDT) Moon 5.9° N.N.W. of Uranus (62° from Sun in morning sky).

(10 UT= 6 EDT) Moon at apogee. Distance 63.50 earth-radii. west of the Sun. See May 21 and 30, and CONJUNCTIONS. ______________________________________________________________________ (20 UT=16 EDT) Mercury 2.1° S.S.E. of Jupiter (26° from Sun in morning sky); ¹ 29 SUN. (11 UT= 7 EDT) Moon 5.4° N.N.W. of Jupiter (39° from Sun in morning sky). magnitudes 0.3 and —2.1. Conjunction in r.a. is 21 hours earlier. o Mon. (20 UT=16 EDT) Moon 3.8° N. of Mars (about 24° from Sun in morning sky). o ²6 030 (20 UT=16 EDT) Mercury, Venus, and Jupiter within circle of diameter 2.05°; 60 60 o (23 UT=19 EDT) Venus, Mars, and Moon within circle of diameter 4.92°; 23° 26° west of the Sun. west of the Sun. Fri. Friday the 13th—supposed to be very unlucky because both the day and the number are unlucky. (In South America the unlucky day is Tuesday and in Italy the ² 31 Tue. ( 1 UT=21 edt) Moon 4.4° N.N.W. of Venus (21° from Sun in morning sky).

(18 UT=14 EDT) Moon 3.7° N. of Mercury (only about 13° from the Sun). unlucky number is 17. In Iran women stay outdoors on the 13th day of the year to (24 UT=20 EDT) Moon 2.0° S. of Pleiades (only about 10° from the Sun). avoid bad luck.) This year has only one Friday-the-13th. They occur every year, either re 50 o 50 o 0o ua S once or twice (each in 42-44 years per century) or 3 times (14 or 15 years per5cenq U S S t Ayou can well tury: common years beginning with Thursday, such as 1981, 1987, 1998, 2009, and On May evenings the Milky Way lies as flat around the horizon as it can get. a So G re PE lying highest, G part 2015, when, occurring in February, it must also occur in March; or, most rarely of all, visualize it as a plane, even though you cannot see it—except possibly the f o leap-years beginning with Sunday, such as 1984 and 2012). Actually, Friday falls on the in Cygnus, to the northeast. If you walk toward that part, you are walking forward in our direction around the Galaxy, with the galactic center on your right.

13th more often than any other day does! (Because Sunday most often falls on the

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Observers’ highlights for May by Fred Schaaf Though tryingly early by the clock and difficultly deep in dawn light, this month’s dance of closely gathered planets is an astonishing complex of wonderful arrangements. In northern lands particularly, sighting all the planets will require haze-free skies and good optical aid. But what should be visible is one of the tightest four-planet gatherings of a lifetime—and much more: two overlapping planetary “triosâ€? (a “trioâ€? is three celestial bodies within a circle less than 5° wide), with each trio lasting for an amazing 8 or 10 days; three pairings of planets in which the pair is separated by less than 1°; two days of the two brightest planets less than 1° from each other; Mercury and Venus within a mere 1½° of each other for two whole weeks; and still more. Each of these sights alone would be one of the few most notable planetary arrangements of a year. Combined all together in one month and small area of the sky, they offer an astonishingly rich and complex show.

Best of the Great May Planet Gathering. A masterful dis-

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cussion and visual presentation of the dawn planet gathering is provided by Guy in CONJUNCTIONS. Read it first, then refer as supplement to this paragraph (in which all figures are precise for 40° N, 75° W but approximately right elsewhere).

Size of full span. The four planets are contained within a 10° (Venus to Jupiter) span on May 1, an astounding minimum span and circle of just under 6° (Mars to Mercury) on May 12, a span of 7½° (Mars to Jupiter) on May 15, a 10° span (Mars to Jupiter) on May 20, and then, as Mercury zooms east, a giant 26° span (Mercury to Jupiter) on May 30. The gathering defined by Jupiter’s journey through it. Jupiter is the planet which glides away from the Sun in this situation with the best combination of speed and steadiness of speed. On May 1 Jupiter is only 23´ from Mars (though very low before sunrise). On May 11 Jupiter is only 37´ from Venus—Venus which stays devotedly between 1° 23´ and 1°30´ from Mercury for a remarkable 14 days (May 7 through 20). In the second half of May, Jupiter, as Venus and Mercury meet Mars in a compact trio (tightest on May 21), moves off to the west

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90˚ 90 May 31, 30 minutes before sunrise 5:04 a.m. EDT (= May 31, 9:04 UT) from the other three planets—which themselves disband by Mercury racing, and Venus creeping, away from Mars back towards the Sun. Overlapping trios.. Mercury-Venus-Jupiter from May 7 to 15 (fits within a circle little more than 2° at most compact on May 11 and 12) and Mercury-Venus-Mars from May 15 to May 25 (fits within a circle little more than 2° at most compact on May 21). Close pairings of the brightest. Venus (magnitude —3.8 and 11″ wide) and Jupiter (magnitude —2.1 and 34″ wide) are 37´ apart on May 11 and 57´ apart on May 12. Period within 5° of each other. Venus and Jupiter, 10 days (May 7-16); Venus and Mars, 21 days (May 13-June 2).

Moon Encounters with the Gathering. See CONJUNCTIONS. At dawn on May 1 on the U.S. East Coast, the Moon is less than 5½° above tightly paired Jupiter and Mars, and the Moon and 4 planets should all fit with a 10° circle (field of ultra-wide binoculars).

Other Highlights. Bright, nearly-all-night Saturn; Eta Aquarid meteor shower (see METEORS).

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Astronomical Calendar 2011

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β Librae, green star?

M5 globular cluster M4 globular cluster Antares, double star M13 globular cluster α Herculis, double star ν Draconis, double star ψ Draconis, double star ε Lyrae, double-double star M57, Ring nebula Albireo, double star

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Page 31

Astronomical Calendar 2011 ch almost

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vernal equinox direction (longitude 0˚)

PLAN of the Moon’s movements projected on the plane of its orbit, as seen from the north; with the Earth held still (so that the Sun is imagined to be going around also, once in the year, 389 times farther away than the Moon’s average distance).

Where the Moon is north of the ecliptic plane its path is shown black; where south, blue. New and full Moons are shown by drawing the Moon, true to scale, plus its umbra, or cone of total shadow. This points radially away from Earth at full Moon, and toward its center at new Moon. Notice the pattern made by the tips of the new-Moon umbrae, reaching to or through Earth only when the Moon is on the perigee (near-in) side of its orbit. This shows that eclipses of the Sun can become total only on that side; on the other side, they can be no more than annular.

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THE MOON Against the backdrop of the stars, we see the Moon move each hour a little more than its own width of ½°. It travels, on average, each day 13.2° (not much less than an hour of right ascension, which is 15°); each month, 401°, or 11⁄9 times around the sky—thus, from its January 1 position around and past this position to the Feb. 1 position.

So in the year it travels about 13.4 times around the sky (passing most stars 13 and some 14 times). But from our moving viewpoint, as we orbit the Sun, the Moon seems to travel around us only 12.3 times; that is, it passes 12 or 13 times through each of its phases in relation to the Sun, such as new Moon or full Moon.

It does not circle around the Earth’s equator (as do many small satellites around larger planets) but behaves more like a companion planet, traveling in the same plane as the Earth— roughly. Its orbit is inclined about 5° to the Earth’s (varying between 4.995° and 5.295° with a period of about half a year). So it appears to follow the ecliptic, departing up to about 5° north or south of it. right ascension 24h 21h 18h +40 +40˚ Vega

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But this orbital plane continually twists (precesses), so that the two nodes, where the orbit crosses the ecliptic, migrate back (westward) at about 19° a year (migrating all around in 18.61 years). This year the ascending node starts at the western end of Sagittarius and moves west across Ophiuchus; and, in the opposite region, the descending node regresses from the western end of Gemini into the middle of Taurus.

This determines how far north and south the Moon ranges in the sky. There are “flat” years, such as 1997, when the ascending node is in Virgo where the ecliptic descends through the celestial equator, so that the Moon’s path curves to less than 19° north and south (roughly the 23.5° inclination of the ecliptic minus the 5° inclination of the Moon). Nine years later there will be a “hilly” year, when the ascending node is in Pisces where the ecliptic also ascends, so that the Moon reaches its furthest possible north and south, 28.72° (the obliquity of the ecliptic plus that of the Moon). (It attains those extremes near the equinoxes: on 2006 March 22 (south) and Sep. 15 (north).) Half way between these are “ecliptic-like” years, when the ascending node is near the top or bottom of the ecliptic, so that the Moon’s path is like a 15h 12h 9h

Declination (vertical) scale exaggerated by 2 01 20 11 20 ---------ecliptic 1997

Jul 1

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+20 +20˚

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-20˚ -20 -30 -30˚ -40˚ -40

t i c Jan 19 LEO cl ip e l l GEMINI Regulus fub 18 new 0

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OPHIUCHUS

LIBRA full SCUTUM E ECLIPS new Jul 15 new Dec 24 Nov 25 3 CAPRICORNUS new full Jan 4 full ECLIPS Jun 15Antares May 17 E Fomalhaut SAGITTARIUS ECLIPSE SCORPIUS

lip t i c new Feb AQUARIUS

CHART of the Moon’s path. Each year it travels 13.4 times around the sky, from west to east (right to left), through the 12 constellations of the zodiac, also Ophiuchus (it can touch Cetus, Orion, Auriga, Hydra, Sextans, Corvus, Crater, Scutum, Pegasus). The two nodes—points where the path

1997

2006 copy of the ecliptic: rising and falling like it about 23° north and south, but displaced east (2001) or west (2011).

In late January 2011 the ascending node passes 270° (18h), so this is one of the middle-state years, when the orbit is like a copy of the ecliptic displaced a few degrees to the west; by the end of the year it is slightly flatter than the eclipic.

The traveling Moon cuts out a swath, wide near the nodes, narrow where it is at its greatest latitudes north and south of the ecliptic (now, in the Pisces and Virgo regions).

At each wide part, the eastward (forward, leftward) edge is where the Moon travels on its January circuit, and the westward (rearward, rightward) edge is its December track.

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2006

full 19 r Ma w e n 27 Sep

new 6 Spica 2 Oct full 8 1 CORVUS Apr

Fe e n w29 Aug

Jul 3

Procyon

ORION

SEXTANS

crosses the ecliptic—shift gradually westward. We show only the paths for January (thick line) and December (thin).

The Moon itself is shown at the instants when it is new (black) and full (white), at 5 times true scale. In each synodic month or lunation (29.5 days) the Moon goes from a

w May 3 full Aldebaran PISCESn full e c l e Dec 10 ipt Apr w Nov 10 ic ECLIPSE 3 full Oct Betelgeuse TAURUS 12

Rigel Sirius

+20˚ +20 +10˚ +10 0˚ -10˚ -10 -20˚ -20 -30 -30˚ -40˚ -40

new-Moon position all around the sky and on to the next new-Moon position; in each calendar month of 30 or 31 daysCanopus its journey overlaps by a bit more. Eclipses happen at Achernar those new and full Moons—the 6th or sometimes 5th of each kind—which are near enough to one of the nodes.

Page 32

distance, in Earth-radii

Astronomical Calendar 2011

There is, as the distance-graph shows, a remarkable relation between the perigees and apogees (extremes

full Feb. 18 Mar. 4 full Mar. 19 Apr. 3 Apr. 18 full

July 30 Aug. 13 Aug. 29

partial eclipse of Sun

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extreme (63.77 Earth-radii = 406,700 km)

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mean (60.3 Earth-radii = 384,401 km)

full

May 17

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partial eclipse of Sun

Jan. 19

May 3

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ri

The orbit is not only tilted but eccentric, as the plan shows. Whereas the nodes move backward, the positions of perigee and apogee migrate generally forward—twice as fast, but irregularly: forward for 5 perigees, then backward for 2 or 3. They progress all the way around in 8.85 years, thus on average 40° a year. This year perigee oscillates between 151° and 235°: the Moon is shining nearest and largest, and moving fastest, when in the direction centered on Virgo.

The egg-shape of the orbit rotates counter-clockwise (as seen from the north). Therefore, looked at perpendicularly as well as edge on, the Moon during the year sweeps out a swath. It is narrow near apogee, because the Moon’s apogee distance is always about the same; wide near perigee, because the perigee distance varies markedly; it is also wide in the quadrants between, where the precessing orbit slopes in and out. Approaching perigee, the Moon is on the inner edge of the swath in January, the outer edge in December; after perigee, vice versa.

Putting the two swaths together, we realize that the Moon carves out a torus (“doughnut”) of space whose width varies in two dimensions.

As the two pairs of positions—the two nodes and the two apsides (perigee and apogee)—revolve in opposite directions, they meet and pass quite frequently. This happened 2009. This year they are about as far apart as they can be. Eclipses have to take place near the nodes. At most of this year’s 6 eclipses the Moon is at middling distances.

All this describes the Moon’s orbit as it appears from the Earth: as if the Earth were fixed. In this frame of reference, the Moon’s motion looks like a near-circle many times repeated. In the wider referenceframe in which Earth and Moon together are journeying around the Sun, the same motion looks like a single near-circle, so much vaster that the Moon’s path is never even convex toward the Sun! (See the MOON’S ORBIT section in the Astronomical Companion.)

of distance) and the syzygies (new and full Moons).

The average period from new to new (or full to full) is the synodic month of 29.53 days. The average period of the distance-wave (perigee to perigee, or apogee to apogee) is the anomalistic month, which is two days shorter at 27.55. The result is like a “beat” between two trains of sound-waves. There is a time of year when new Moon is coinciding with perigee, and full Moon with apogee. Last year it was in August; it now falls in September-October. Then, 6½ months later (now in March), comes a time when the reverse happens: full Moon occurs near perigee.

Each year, each of these times shifts later by a bit more than a month.

At the syzygies, the three bodies are in a straight line, Sun-Moon-Earth or Sun-Earth-Moon.

The Moon’s instantaneous orbit is squeezed toward this line: that is, it becomes a more eccentric ellipse. The effect is less when the Moon is farther out, Earth’s pull on it being less; so the apogee distance increases, but not much. At perigee, however, the Moon comes nearly a whole Earth-diameter (about 12,000 kilometers) nearer in toward us if it happens to be directly toward, or away from, the Sun. This enhances any total solar eclipse that occurs near to perigee. This year the only such is the partial eclipse of Nov. 25.

Tides, too, are strongly affected by the relation between perigee and syzygy. High tide comes twice a day, once under the Moon (actually somewhat behind it, because friction with the solid Earth delays the water) and once when the Moon is on the Earth’s opposite side.

The Sun also has a tidal pull on the Earth, rather less than half that of the Moon. So at or just after the new and full Moons of each month, when Sun, Moon and Earth are in line, the tide is amplified into a “spring tide” (nothing to do with the season called spring).

There is a tidal swelling on both sides of the Earth.

So, whether spring tide is at a new or a full Moon, there is one flood tide under the noonday Sun, the other at midnight. But one kind of midnight spring tide is moonlit, the other swells in darkness.

When the Moon is near—that is, at perigee—its tidal pull is greater. Moreover, perigees, as we have just seen, are much nearer perigees when they coincide with new or full Moon. Thus it follows that when these times of coincidence arrive we expect the tides of greatest amplitude: highest high tides and lowest low tides of the year. These perigean spring tides may cause coastal flooding, especially if they happen to be accompanied by storms; they may even trigger earthquakes and volcanoes.

Here are this year’s closest coincidences, with their hours in Universal Time, and the Moon’s perigee distances in kilometers (as given in Meeus’s Astronomical Tables), which are the year’s nearest:

e

The swath is really wider than in the chart, for two reasons: the Moon itself is half a degree wide; and as seen from places at the north end of the Earth it appears nearly a degree farther south (or from the south of the Earth nearly a degree farther north).

Stars within this swath can get occulted (hidden) by the Moon, as seen from at least some part of the Earth. Four of the stars in the occultable band— Aldebaran, Regulus, Spica, Antares—are of first magnitude. This year the Moon’s track misses all four: it continues to pass north of Aldebaran, south of Regulus and Spica, north of Antares. It continues, at first, to sweep the southern edge of the Pleiades.

56

(Earth's equatorial radius: 6378 km = 3963 miles)

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Sep. 12 new Sep. 27 full Oct. 12 Oct. 26 new Nov. 10

partial eclipse of Sun

full

Nov. 25 new

total eclipse of Moon

Dec. 10 Dec. 24

full

new

GRAPH of the Moon’s varying distance through the year. The curve is blue when the Moon is south of the ecliptic. The Moon is shown to the same scale as that used for distance, at the moments of its cardinal phases—new (dark side toward us), first quarter (sunlit side to west), full (sunlit side toward us), last quarter (sunlit side to east).

For the mean distance, Allen’s Astrophysical Quantities (1999) gives 384,401±1 km (60.27 Earth-radii); Meeus in Mathematical Astronomy Morsels (1997) gives 10 values, ranging from 381,546 to 385,001 km (59.82 to 60.36 e.r.), depending on what we mean by “mean distance”!

Mar. 19 18:60 perigee — Mar. 19 18:10 full —0.8 hr 356575 Sep. 28 1:13 perigee — Sep. 27 11: 8 new -14.1 hr 356557 Oct. 26 12:35 perigee — Oct. 26 19:56 new 7.3 hr 357052

Even closer perigees are: 1993 Mar. 8 (356,528 km); 2016 Nov. 14 (356,509).

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MOON’S TRAVEL in a sample day, Dec. 10, from 0h to 24h UT, shown at 3-hour intervals.

The Moon is at true scale. For each time, it is plotted (1) geocentrically, as if seen from the center of the Earth (the evenly spaced Moons connected by a line); (2) topographically, as seen from Philadelphia, 40° north, 75° west, and (3) from Wellington, New Zealand, 41° south, 175° east. The topocentric displacements are caused by parallax (as when you move your head to look at something from different viewpoints), which affects the Moon strongly because of its relative nearness. It appears farther south from viewpoints north of where it is overhead; and vice versa. So its north-southness changes as you are carried around to different positions on the tilted Earth. And it appears farther east (left, from our northern hemisphere) if you are west of where it is overhead, especially at moonrise; as it moves through the sky toward setting it lags westward behind its geocentric position, because you are now looking backward to it. Parallax also affects its distance: it is up to 4000 miles nearer, thus appearing larger, when high in the sky; more distant when you see it low to the horizon (though then, by the “Moon illusion,” appearing larger!). When rotation has carried you around to the other side of the Earth, the Moon is yet more distant

and of course invisible. To indicate that some Moons are invisible we color them blue.

This applies also to the Moon as “seen” from the center of the Earth.

The scale of the chart is 1.5 cm to 1°. To save vertical space, it is plotted in ecliptic latitude and longitude. The more familiar equatorial coordinates (lines of right ascension and declination) are also shown, slanting and curving in relation to the ecliptic system.

The ecliptic itself is marked by dashes 0.25° long. At 7:02 UT the Moon is at descending node: its center crosses the ecliptic at its inclination-angle of about 5°.

At 14:37 UT the Moon comes to its Full position, only 7½ hours after crossing the ecliptic, so it passes through Earth’s shadow. For New Zealand this is 2:30 in the morning, so the eclipsed Moon is in the sky, if low to the north; for North America it is around sunrise and only the far northwest lingers to see the middle of the eclipse.

The patch of sky where all this happens is about one hour of right ascension, or one day’s Moon-travel, back west from where it was during last year’s Dec. 21 eclipse (see this page in Ast. Cal. 2010). Zeta Tauri (the star at the tip of the Bull’s northern horn) and the Crab Nebula were at the beginning of that picture and the end of this.

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Astronomical Calendar 2011

DARK OF THE MOON This table shows the hours of deep night. Each line represents the night between this day and the next. The figure for each night and latitude is the number of hours between the end of evening astronomical twilight and the beginning of morning astronomical twilight when the Moon is not in the sky. A blank means that the Moon is in the sky all night. All-blank times (as around Jan. 19) are when the Moon is full. At the beginning of each moondark patch (as around Jan. 22) the dark hours are at the beginning of the night (before the Moon Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Jan. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Mar. Mar.

lat. —35° 1 5.7 2 6.0 3 6.0 4 6.1 5 6.1 6 6.1 7 6.0 8 5.6 9 5.2 10 4.7 11 4.3 12 3.8 13 3.3 14 2.6 15 1.9 16 1.0 17 18 19 f 20 21 22 23 .4 24 1.0 25 1.6 26 2.3 27 3.1 28 3.9 29 4.8 30 5.8 31 6.8 1 7.0 2 7.1 3 7.1 4 7.1 5 7.2 6 7.2 7 6.9 8 6.4 9 5.9 10 5.3 11 4.6 12 3.8 13 2.9 14 1.9 15 .8 16 17 18 f 19 20 21 .2 22 .9 23 1.6 24 2.5 25 3.4 26 4.4 27 5.4 28 6.4 1 7.4 2 8.3

0° 8.7 9.4 9.4 9.4 9.4 8.8 8.1 7.4 6.7 6.0 5.4 4.6 3.9 3.1 2.2 1.2 .3 u .3 1.2 2.0 2.9 3.8 4.7 5.6 6.5 7.4 8.3 9.2 9.5 9.5 9.5 9.5 8.9 8.2 7.6 6.9 6.1 5.3 4.5 3.6 2.7 1.7 .8 u .8 1.7 2.6 3.5 4.5 5.4 6.3 7.2 8.0 8.8 9.5

30° 10.5 10.9 10.9 10.9 10.9 10.0 9.1 8.2 7.4 6.5 5.6 4.7 3.8 2.8 1.8 .8

40° 11.2 11.4 11.3 11.3 11.3 10.5 9.5 8.5 7.5 6.6 5.6 4.6 3.6 2.5 1.5 .5

l

l

.6 1.7 2.8 3.9 5.0 6.0 7.1 8.1 9.0 9.8 10.5 10.5 10.5 10.4 10.3 9.4 8.5 7.6 6.7 5.8 4.8 3.9 2.9 2.0 1.1 .3

.6 1.8 3.0 4.2 5.4 6.6 7.7 8.7 9.6 10.4 10.8 10.7 10.7 10.7 10.5 9.5 8.5 7.5 6.5 5.5 4.5 3.5 2.5 1.5 .7

l .2 1.3 2.4 3.5 4.6 5.6 6.6 7.4 8.2 8.8 9.4 9.8

l .2 1.4 2.7 3.9 5.0 6.1 7.0 7.9 8.5 9.1 9.6 9.6

50° 11.9 11.9 11.8 11.8 11.8 11.1 9.9 8.8 7.7 6.6 5.5 4.4 3.2 2.1 1.0

.6 1.9 3.3 4.6 5.9 7.2 8.4 9.5 10.4 11.0 11.0 10.9 10.9 10.8 10.7 9.6 8.4 7.3 6.2 5.1 3.9 2.8 1.8 .8 .1

.2 1.6 2.9 4.3 5.5 6.7 7.6 8.4 9.0 9.5 9.4 9.4

Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Mar. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. Apr. May May

lat.

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2

—35° 8.3 8.4 8.4 8.5 8.5 8.4 7.9 7.2 6.5 5.6 4.7 3.6 2.5 1.3 .2 f .2 1.0 1.9 2.9 3.9 5.0 6.0 6.9 7.9 8.8 9.5 9.5 9.6 9.6 9.6 9.6 8.9 8.1 7.2 6.2 5.1 4.0 2.9 1.8 .6 f .3 1.3 2.3 3.4 4.4 5.4 6.4 7.3 8.2 9.1 10.1 10.5 10.5

0° 9.6 9.6 9.6 9.6 8.9 8.2 7.4 6.6 5.7 4.8 3.9 3.0 2.1 1.1 .2 u .5 1.4 2.4 3.4 4.3 5.2 6.1 6.9 7.6 8.3 9.0 9.6 9.6 9.6 9.6 9.3 8.5 7.6 6.8 5.9 5.0 4.1 3.2 2.3 1.5 .6 u .2 1.2 2.2 3.2 4.0 4.9 5.6 6.3 7.0 7.7 8.4 9.1 9.5 9.5

30° 9.7 9.7 9.7 9.3 8.4 7.5 6.5 5.6 4.6 3.7 2.8 2.0 1.3 .5

40° 9.6 9.6 9.5 9.1 8.1 7.1 6.0 5.0 4.0 3.1 2.2 1.5 .8 .2

l .9 2.0 3.1 4.1 5.0 5.8 6.5 7.1 7.7 8.2 8.7 8.8 8.8 8.7 8.7 8.1 7.1 6.2 5.2 4.4 3.5 2.8 2.1 1.4 .8 .1 l .4 1.5 2.5 3.4 4.1 4.8 5.3 5.9 6.3 6.8 7.3 7.8 7.8 7.7

50° 9.3 9.2 9.2 8.7 7.6 6.4 5.3 4.1 3.1 2.1 1.3 .6 .1

l 1.0 2.2 3.4 4.4 5.3 6.0 6.6 7.2 7.6 8.0 8.3 8.2 8.2 8.1 8.1 7.4 6.3 5.3 4.4 3.5 2.7 2.1 1.4 .9 .3

l .4 1.5 2.5 3.3 4.0 4.6 5.0 5.5 5.9 6.2 6.6 6.7 6.6 6.6

1.0 2.4 3.6 4.7 5.5 6.2 6.7 7.1 7.4 7.4 7.3 7.3 7.2 7.1 7.0 6.3 5.2 4.1 3.1 2.3 1.5 .9 .4

.2 1.4 2.3 3.1 3.7 4.1 4.5 4.7 5.0 4.9 4.8 4.7 4.6 4.5

STRIP-CHART OF THE MOON The wavy chart shows, for the whole year, the course and changing appearance of the Moon. It advances eastward about 13.2° per day, thus circumnavigating the sky about 13.4 times.

It keeps within about 5° of the ecliptic. (The ecliptic is the yellow curve; the celestial equator is the level red line.) The chart is equatorially based, so that you can see the Moon moving north and south in declination; but the selection of the celestial map shown is a band about 24° wide centered on the ecliptic. The boundaries of the constellations are shown. Like most of the planets, the Moon visits the twelve constellations of the traditional zodiac plus Ophiuchus, sometimes Cetus, Orion, Auriga, Hydra, Sextans, Corvus, Crater, Scutum, Pegasus (see Jean Meeus, More Mathematical Astronomy Morsels, p. 333).

The positions of the Moon are for each day at 0h Universal Time (midnight in western Europe). This is 7 p.m.

American EST, or 8 p.m. EDT, on the previous date. In other words, for the evening of a given day in America the nearest Moon-picture will be that for the next date.

And the positions are as seen from the center of the Earth, without applying parallax. As seen from northern latitudes such as North America and Europe the Moon appeara up to a degree farther south than the geocentric positions shown; as seen from the southern hemisphere, it is displaced north.

The scale is about 0.7 millimeter per degree. The Moon is shown 16 times larger than its apparent size. However, the difference from its mean width of ½° is also exaggerated.

(The width shown is: the actual width plus 2 times the difference between the actual and mean widths, all multiplied by 16.) The purpose is to make clearer how the apparent size varies according to whether the Moon is near or far in its elliptical orbit. This year it is nearest, therefore appearing largest. on Mar. 19, and farthest and smallest, on Apr. 2— almost the passage between a full Moon and the next new Moon (see the MOON distance graph).

A tick shows the Moon’s own north pole. (That is, the

May May May May May May May May May May May May May May May May May May May May May May May May May May May May May June June June June June June June June June June June June June June June June June June June June June June June June June June June June June June July July

lat.

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2

—35° 10.5 10.5 10.4 9.6 8.6 7.6 6.5 5.4 4.3 3.2 2.0 .9 f .4 1.5 2.5 3.5 4.5 5.5 6.4 7.3 8.2 9.2 10.1 11.0 11.1 11.1 11.1 11.0 9.9 8.9 7.8 6.7 5.6 4.5 3.4 2.2 1.0

0° 9.5 9.5 8.7 7.8 6.9 6.0 5.2 4.3 3.5 2.6 1.8 .9 u

30° 7.7 7.7 6.8 5.9 5.0 4.3 3.6 2.9 2.3 1.7 1.0 .3 l

.9 1.8 2.7 3.5 4.2 4.9 5.6 6.3 7.0 7.7 8.4 9.2 9.4 9.4 9.4 9.0 8.1 7.2 6.4 5.5 4.7 3.9 3.0 2.1 1.2 .2

.7 1.6 2.3 2.9 3.4 3.9 4.4 4.9 5.4 5.9 6.5 6.9 6.9 6.9 6.9 6.8 6.0 5.3 4.6 4.0 3.4 2.8 2.1 1.5 .7

f

u

l

.3 1.3 2.3 3.3 4.2 5.2 6.1 7.0 7.9 8.9 9.8 10.8 11.2 11.2 11.1 11.1

.4 1.2 2.0 2.7 3.4 4.1 4.8 5.5 6.2 7.0 7.8 8.7 9.4 9.4 9.4 9.4

.5 1.1 1.7 2.2 2.7 3.2 3.7 4.2 4.9 5.6 6.4 6.7 6.7 6.8 6.8

40° 6.5 6.5 5.7 4.8 4.0 3.3 2.6 2.1 1.5 1.0 .5

50° 4.4 4.3 3.9 3.0 2.2 1.6 1.0 .6 .1

l .4 1.2 1.8 2.4 2.8 3.2 3.6 4.0 4.4 4.8 5.3 5.3 5.2 5.2 5.2 5.1 4.7 4.1 3.5 3.0 2.5 2.0 1.4 .8 .2 l

.4 .9 1.3 1.7 2.1 2.5 3.0 3.6 4.2 4.9 4.9 5.0 5.0 5.0

.2 .6 1.0 1.3 1.6 1.7 1.6 1.4 1.2 1.0 .7 .2

rises); toward the end of the patch the dark window is at the end of the night, after the Moon sets. Around the middle of each patch (as Jan. 1 to 7) the Moon is no problem even when it is in the sky, since it is thin. At latitude 50° in June and early July, twilight lasts all night.

You can use the table to choose nights when it is worth traveling out to your dark observing site. Saturday nights (between Saturday and Sunday) are in boldface.

The table’s space-saving format suggests an interesting alternative calendar of six 61-day months! In leap-years such as 2008 and 2012 these “bimonths” are equal in length; in the other years only one is a day shorter.

July July July July July July July July July July July July July July July July July July July July July July July July July July July July July Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Aug. Sep.

lat.

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1

—35° 10.0 8.9 7.8 6.7 5.6 4.4 3.3 2.2 1.1 .1

0° 8.5 7.7 6.9 6.0 5.2 4.3 3.4 2.5 1.5 .5

30° 6.7 6.1 5.5 4.9 4.3 3.6 2.9 2.1 1.2 .3

40° 5.0 5.0 4.5 4.1 3.6 3.0 2.4 1.7 .8

f

u

l

l

.9 1.9 2.8 3.7 4.6 5.5 6.5 7.4 8.3 9.3 10.1 10.8 10.8 10.7 10.7 9.8 8.7 7.5 6.4 5.2 4.1 3.0 2.0 1.1 .3

.6 1.3 2.0 2.7 3.4 4.1 4.9 5.6 6.5 7.4 8.3 9.2 9.5 9.5 9.5 9.0 8.2 7.3 6.4 5.5 4.6 3.6 2.7 1.7 .9 .0

.3 .8 1.3 1.8 2.4 3.0 3.6 4.4 5.3 6.2 7.3 7.4 7.4 7.4 7.4 7.2 6.6 6.0 5.3 4.5 3.7 2.8 1.8 .8

.4 .9 1.3 1.9 2.5 3.2 4.1 5.0 5.9 6.0 6.0 6.1 6.1 6.2 6.1 5.6 5.0 4.3 3.5 2.6 1.7 .6

f

u

l

l

.4 1.3 2.2 3.1 4.0 4.9 5.9 6.8 7.6 8.4 9.2 9.9 10.0 9.9 9.9 9.3 8.1 6.9

.0 .7 1.4 2.1 2.9 3.6 4.4 5.3 6.2 7.1 8.0 8.9 9.6 9.6 9.6 9.4 8.5 7.6

.3 .8 1.4 2.1 2.8 3.6 4.5 5.5 6.5 7.6 8.3 8.4 8.4 8.4 8.4 7.7

.1 .6 1.2 1.9 2.7 3.6 4.6 5.7 6.9 7.5 7.6 7.6 7.7 7.7 7.6

50°

.4 1.1 1.9 3.0 3.2 3.3 3.4 3.5 3.6 3.7 3.8 4.0 4.1 3.7 3.0 2.2 1.2 .2

.5 1.2 2.1 3.2 4.5 5.8 6.1 6.2 6.3 6.4 6.5 6.5

pole of its rotational axis: it does rotate, but in the same period as it revolves around the Earth, thus keeping approximately the same face to the Earth.) Lunar east is to the right, as on a map or globe of the Earth.

The instants when the Moon is at its cardinal phases are shown by white bars—thick for new and full Moon, thinner for first and last quarter—thus marking the four segments of each synodic month (lunation) from New Moon around to New Moon. The phases trend diagonally across the page, as the Earth-Moon system moves around the Sun. The sky background is shown becoming darker around full Moon, when the Moon is mostly seen at night, and lighter during the phases when it is seen, if at all, in twilight and daylight. The pictorial darkness is inversely proportional to the illuminated fraction of the Moon.

When the Moon is almost certainly invisible (with less than 0.02 of its width sunlit), a day or so before or after new Moon, only a thin semicircle facing the Sun is shown. At new Moon the Moon passes across the Sun’s face at the eclipse of Jan. 4, then north until it again crosses the Sun’s face on July 1, then south of it till the unusual third solar eclipse (Nov. 25).

Eclipses are shown for the time of day they occur (rather than at 0h of the date). For lunar eclipses, the Earth’s umbra is shown deep brown. For the partial solar eclipse, the Moon silhouetted against the Sun is shown blue (like the surrounding sky).

Also shown are the six bright stars near the ecliptic (and the Pleiades); and the five naked-eye planets (Mercury, Venus, Mars, Jupiter, Saturn), where they are when the Moon passes near them. The symbols are proportional in diameter to brightness: asterisks for the planets; circles for the stars, colored according to their spectral types. Because the Moon’s size is so greatly exaggerated, we cannot show its more exact relations to the other bodies at these appulses.

The planets and stars, though really far beyond the Moon, are shown as if in front of it, otherwise they would often be hidden. The Moon does in fact this year occult Mercury on Oct. 28, Venus on June 30, and Mars on July 27 (see OCCULTATIONS).

Four of the stars (Antares, Spica, Regulus, and

Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Sep. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Oct. Nov.

lat. —35° 2 5.7 3 4.6 4 3.5 5 2.6 6 1.8 7 1.1 8 .5 9 10 11 12 f 13 14 .7 15 1.6 16 2.5 17 3.4 18 4.3 19 5.2 20 6.0 21 6.7 22 7.4 23 8.0 24 8.6 25 8.9 26 8.9 27 8.9 28 8.6 29 7.4 30 6.2 1 5.0 2 4.0 3 3.2 4 2.4 5 1.8 6 1.2 7 .6 8 .1 9 10 11 12 f 13 14 .9 15 1.8 16 2.6 17 3.5 18 4.2 19 4.9 20 5.5 21 6.1 22 6.7 23 7.2 24 7.7 25 7.7 26 7.6 27 7.6 28 6.7 29 5.6 30 4.6 31 3.8 1 3.1

0° 6.6 5.7 4.7 3.7 2.8 2.0 1.2 .4 u .3 1.0 1.7 2.5 3.3 4.2 5.1 6.0 6.8 7.7 8.6 9.5 9.6 9.6 9.6 8.7 7.7 6.7 5.7 4.8 3.9 3.1 2.3 1.6 .8 .2

30° 6.9 6.1 5.2 4.2 3.3 2.3 1.3 .4 l .0 .7 1.4 2.1 3.0 3.9 4.9 5.9 7.0 8.1 9.3 9.3 9.4 9.4 9.3 8.5 7.6 6.6 5.6 4.6 3.7 2.8 1.8 1.0 .1

40° 6.9 6.1 5.3 4.3 3.3 2.3 1.3 .3

50° 6.6 6.2 5.4 4.4 3.4 2.3 1.1 .0

l

.1 .7 1.4 2.3 3.2 4.3 5.4 6.6 7.8 9.0 9.0 9.0 9.1 9.1 8.8 7.9 6.9 5.9 4.9 3.9 2.9 1.9 .9

u

l

l

.6 1.4 2.2 3.1 4.0 4.8 5.7 6.5 7.3 8.2 9.1 9.5 9.5 9.5 8.8 7.8 6.8 5.9 5.0

.6 1.4 2.3 3.3 4.3 5.3 6.3 7.4 8.5 9.7 10.2 10.2 10.2 10.1 9.1 8.1 7.1 6.1

.2 1.0 1.8 2.8 3.9 5.0 6.2 7.4 8.6 9.8 10.2 10.3 10.3 10.3 9.6 8.6 7.5 6.5

.4 1.2 2.2 3.3 4.6 5.9 7.3 8.4 8.4 8.5 8.6 8.6 8.7 8.3 7.3 6.3 5.2 4.1 3.0 1.9 .8

.2 1.1 2.2 3.3 4.6 5.9 7.2 8.6 10.0 10.2 10.3 10.3 10.4 10.3 9.2 8.1 6.9

Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Nov. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec.

lat. —35° 2 2.5 3 2.0 4 1.4 5 1.0 6 .5 7 8 9 10 f 11 12 .0 13 .8 14 1.6 15 2.3 16 2.9 17 3.5 18 4.0 19 4.6 20 5.1 21 5.7 22 6.4 23 6.5 24 6.4 25 6.4 26 6.4 27 5.5 28 4.8 29 4.1 30 3.5 1 3.0 2 2.5 3 2.1 4 1.6 5 1.1 6 .5 7 8 9 10 f 11 12 13 .4 14 1.0 15 1.6 16 2.1 17 2.6 18 3.2 19 3.8 20 4.5 21 5.3 22 5.9 23 5.9 24 5.9 25 5.9 26 5.9 27 5.7 28 5.1 29 4.6 30 4.2 31 3.7

0° 4.2 3.5 2.8 2.1 1.4 .7

30° 5.1 4.2 3.3 2.5 1.6 .7

40° 5.4 4.4 3.5 2.5 1.6 .6

u

l

l

.2 1.0 1.9 2.7 3.5 4.3 5.1 6.0 6.8 7.7 8.6 9.4 9.4 9.4 9.1 8.2 7.2 6.4 5.6 4.9 4.2 3.5 2.8 2.1 1.4 .6

.6 1.5 2.5 3.5 4.5 5.5 6.5 7.6 8.7 9.9 10.7 10.7 10.8 10.8 9.7 8.7 7.7 6.7 5.8 4.9 4.0 3.2 2.3 1.4 .5

.3 1.2 2.2 3.3 4.4 5.5 6.7 7.9 9.1 10.3 11.1 11.1 11.1 11.2 10.3 9.2 8.1 7.1 6.1 5.1 4.1 3.2 2.2 1.3 .3

u

l

l

.4 1.3 2.1 2.9 3.7 4.5 5.3 6.2 7.1 8.1 9.1 9.4 9.4 9.4 8.8 8.0 7.2 6.5 5.8 5.1

.4 1.4 2.4 3.4 4.4 5.4 6.4 7.5 8.6 9.7 10.8 10.9 10.9 10.9 10.2 9.2 8.2 7.3 6.4 5.5

.2 1.3 2.3 3.4 4.5 5.7 6.8 8.0 9.2 10.4 11.4 11.4 11.4 11.4 10.8 9.7 8.6 7.6 6.6 5.6

50° 5.8 4.7 3.6 2.6 1.5 .4

.7 1.8 3.0 4.2 5.5 6.8 8.1 9.5 10.9 11.5 11.5 11.5 11.6 11.1 9.9 8.7 7.5 6.4 5.3 4.2 3.2 2.1 1.1 .0

1.0 2.3 3.5 4.7 6.0 7.3 8.6 9.9 11.2 11.9 11.9 11.9 11.9 11.4 10.2 9.0 7.9 6.8 5.7

Aldebaran) lie near enough to the ecliptic to be occulted, but this year none of them get occulted.

Libration, the apparent “rocking” of the Moon, brings some of it into our view beyond the mean limb (edge), so that over time we get to see not just 50% of the Moon but 59%. This is shown by the red spots. Each is at the point most librated toward us, and its size is proportional to the amount of the libration. By pointing your telescope at the larger of these spots, you will be able to peer quite far past the average limb into the highly foreshortened features of the Luna Incognita (“unknown Moon”) on the Moon’s far side.

The amount can vary from zero up to about 10.5°. This year it ranges between 2° on Dec. 22 and 9.3° on Oct. 21.

That is, on Oct, 21 an extra 9.3/360 of the Moon’s circumference comes into view. Look for this strip of Luna Incognita beyond Mare Crisium, as the first-quarter Moon cruises south of Spica! This unfortunately is on the dark limb of the firstquarter Moon; look for other large red spots on the sunlit limb of conveniently seen Moons, such as Apr. 28.

Around that date your telescope can see new mountains past the northwest limb of the last-quarter Moon.

You can search the diagram for other dates when large dots fall on the bright limb, preferably at times when the Moon is waxing (bright limb to the west or right) and therefore in the early-night sky.

The north-south component of libration is caused by the inclination of the Moon’s orbit: when it is traveling south of the ecliptic we are looking “down” on it. (This is why the libration dots are all on the same side of the Moon’s center as the ecliptic.) A side-to-side component is caused by the Moon’s not-quite-circular orbit: it moves faster when closer to us, but keeps rotating at the same rate. There is also a small physical libration caused by the Moon’s non-spherical shape.

Finally, there is a diurnal (daily) libration, not showable here, for each observer, carried around to different points of view by the rotation of the Earth’s surface. (You see farther around the Moon’s left when it is setting, because the Earth’s center is to your right. And vice versa.) Libration determines the figure the Moon shows during a solar eclipse—the profile of mountains silhouetted against the Sun.

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Astronomical Calendar 2011

24h

23h

22h

21h

20h

18h

19h

17h

16h

15h

14h

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b

Astronomical Calendar 2011 ant um

st reate e ---------g eclips

2011 June 1 21:00 UT

120˚E

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June 1—Partial eclipse of the Sun The Moon drops back around the Earth’s sunward side nearly a whole day before it descends to its node through the ecliptic plane; therefore its shadow brushes only the northern rim of the Earth. First, the outer shadow, the penumbra, meets the part of the Earth’s front that is advancing into sunlight; the point of first contact happens to be very near to Vladivostok, Russia’s largest port city on the Pacific coast.

Local clocks here will read 5:25 a.m. on the morning of June 2, as this will happen to the west of the International Date Line. Here theoretically the Sun could be seen to rise with the beginning of a dent in its upper left edge.

The penumbra spreads onto the Earth, sliding slightly southward in space because of the Moon’s descending motion toward the node; but geographically it is pushed first northward and then southward across the surface because of the Earth’s orientation at this time of year, with its north pole tilted toward the Sun. The axis of the Moon’s shadow never hits the surface, passing about .213 of the Earth’s radius, or

(relative to Ea

rtj cemter)

1,358 kilometers, above Cheshskaya Bay and the Bolshezemelskaya Tundra of far northwestern Russia. Here, the Sun is seen to dip right to the northern horizon—at the “midnight” point of its twenty-four hour Arctic day—before climbing again; and for the minutes of the eclipse, with its upper three-fifths bitten away, it takes the appearance of some huge boat sailing out over the icy Barents Sea. The umbra or total shadow, even if aimed lower, would not reach the Earth: it stops in space because of the Moon’s somewhat greater than average distance at this time, so even if you had the superhuman ability to jump 1,358 kilometers upward you would see only an annular or ring-shaped eclipse—the Moon failing to cover the whole Sun. The zone of visibility for this eclipse also covers parts of northeast Asia, which will see the eclipse during the morning hours of June 2 with the Sun sloping up the sky. The penumbra will then cross the International Date Line heading east, the calendar shifting back one day to June 1. The eclipse will also be available to the northern two-thirds of Alaska (an early

Partial solar eclipse of June 1 All times U.T. May 27, 10:10—Moon at apogee: 405,003 km (251,657 mi) from Earth.

Jun. 1, 19:25—partial eclipse begins: first contact of Moon’s penumbral cone with Earth, at local sunrise.

21:03—New Moon (conjunction of Moon with Sun in ecliptic longitude): Moon’s center is exactly north of Sun’s as measured perpendicularly to ecliptic.

21:16—greatest eclipse: Moon passes nearest to center of Sun. The magnitude of the eclipse is 0.6013; that is, the Moon covers this fraction of the Sun’s diameter.

21:22—conjunction of Moon and Sun in right ascension: Moon’s center passes exactly north of Sun’s as measured perpendicularly to Earth’s equator. Center of eclipse takes place at local apparent noon, with Sun and Moon on meridian.

23:07—partial eclipse ends: last contact of Moon’s penumbral cone with Earth, at local sunset.

Jun. 2, 20:20—Moon’s center reaches descending node through ecliptic.

Jun. 12, 01:35—Moon at perigee: 367,189 km (228,160 mi) from Earth.

Jun. 14, 21:02—middle of eclipse season; Sun at same longitude as true descending node.

This is eclipse no. 68 of the 72 in solar saros series 118.

afternoon event), as well as northern and eastern portions of Canada, which will see the eclipse during the course of their afternoon, as the Sun slowly descends toward the west-northwest horizon. Greenland and Iceland are also within the eclipse zone, the latter getting a view just before the Sun begins to set in their late evening. The penumbral shadow quits the surface over the open waters of the Atlantic to the east of Newfoundland, as the Sun passes out of sight.

Notice in our timetable that this is “eclipse no. 68 of the 72 in saros series 118.” Every eclipse belongs to a series of similar ones 18.03 years apart (the time span called the saros); similar, but evolving. This series is a very old one, that started as far back as the year 803 and is nearing the end of its life: at each eclipse in this series the Moon’s shadow sweeps slightly farther north, so that the next ones, in 2029, 2047 and so on, will be progressively slighter and concentrated more on the Arctic region, until after the last very slight one on July 15, 2083, the shadow at the corresponding New Moon in July 2101 will miss the Earth altogether.

Local circumstances for June 1. * means Daylight Saving Time is in effect. ** means the calendar date is June 2. time 1st max. last zone contact eclipse mag. alt. contact Sapporo UT+9h** 4:27 am 4:50 am 0.086 7.7° 5:15 am Fairbanks UT-9h* 12:48 pm 1:09 pm 0.035 11.9° 1:31 pm Baker Lake UT-6h* 4:30 pm 5:04 pm 0.112 12.8° 5:37 pm Churchill UT-6h* 5:02 pm 5:17 pm 0.020 13.0° 5:31 pm Charlottetown UT-4h* 7:32 pm 7:45 pm 0.025 10.1° 7:59 pm St. John’s UT-3.5hm* 7:41 pm 8:09 pm 0.127 4.8° 8:37 pm Thule UT-4h* 5:57 pm 6:48 pm 0.376 24.0º 7:38 pm Reykjavik UT 9:14 pm 10:01 pm 0.462 4.9º 10:48 pm

Eureka moments Archimedes got into a bathtub, realized that the rise of the water must correspond to his own volume, saw that this is a method to measure the volume of any object, and exclaimed “Heurêka!—I have found [it]!” His exhilaration may, or may not, have had him shouting it as he jumped out and ran naked through the streets.

Isaac Newton told his biographer William Stukeley in

1726 that in 1666 “he was just in the same situation [sitting in a garden under the shade of an apple tree], as when formerly the notion of gravitation came into his mind. Why shd that apple always descend to the ground, thought he to himself, occasion’d by the fall of an apple . . .” The wording does imply that he saw at least one apple actually fall, but there is no evidence for the legend that it fell on his head.

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48 2011 Astronomical Calendar 2011 45o

45 o

SUNSET sky -- latitude 40˚ 40 NORTH 40 o

35o

35 o

c

30o

e

altitude

40o

l

e s

t

ia

l q

20 Jan 12 1

e

25o

30 o

u

25 o

a to r

elongation east Mar 23

21

20o

11

Mercury (Mar-Apr)

De c1

Venu s

11

(Oc t-N

No v1 3

Nov 1

11

ry

Oct 1

Oct 21

10 o

(Jun-Aug)

21

Mercu

21

1 Aug

5o

Mercury

Nov 1

11

elongation east Nov 14 21

N appov 1 ulse

10o

15 o

Jul 1

r1 Ap

21

11

Jul 20 elongation east 21 11

15o

20 o

21

21

5o

11 Sep 1

ov)

Aug 2 1

SSW

SW

WSW

A Mercuug 17 ry-Ven us

11

horizon

W

WNW

Venus superior conjunction with Sun Aug 16

2011 45o

45 o

SUNSET sky -- latitude 35˚ 35 south 40o

40 o

35o

35 o

elongation east Nov 14

s

Jul 20 elongation east

21

20 o

1

Nov 1 and 13 appulses

Mercury

21 11 21

Oc

(Oct-Nov)

(Jun-Aug)

Ve n t1

o

15 o

Jul 1

o

us

1 t1 Oc

21

10 o 21

11

5o

11

Mar 23 elongation east

Se p1

Mercury

5o

(Mar)

21

SW

WSW

horizon

W

s Venun Su h it w ction Aug 16 onjun rior c

WNW

NW

supe

HORIZON SCENES show the visits of Mercury and Venus to the evening and morning skies. The top charts show the sky as seen from our northern hemisphere, at the time of sunset (left) and sunrise (right). The lower charts show how things appear (very differently) at the same times for observers in the southern hemisphere.

Venus is so bright that it can often be found before sunset, or after sunrise. For Mercury you must wait, probably half or three-quarters of an hour, for the sky to darken (or be looking the same amount of time before sunrise).

You can imagine the changed situation at, say, an hour

25 o

1

11

ov

v1 No

21

le

g Au

N

o

Mercury 10

e

l

1 21 1

15

c

D 11

20

21

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30 o

21

ec

t

u

r

Ju n

25o

2012 Jan 1

q

to

altitude

e

a

11

30

o

after sunset by mentally raising the horizon-line about 12°.

The sky will be darker, but the planets will be lower, more obstructed by atmosphere and trees, or even below the horizon.

The upper charts are for latitude 40° north (San Francisco, Philadelphia, Madrid, Istanbul, Beijing). The lower charts are for 35° south, roughly the latitude of Buenos Aires, Cape Town, Sydney, and Auckland.

Longitude makes little difference, because planets do not move as fast as the Moon. If you are half way around the world, the planet will (by the corresponding time at your location) have moved only half the distance betwen two

dots. But latitude makes its usual great difference. If you are farther north, you must imagine the horizon tilted upward on the south like a seesaw, around the Sun’s position as a pivot. Or, which is the same thing, you will find the equator lying flatter, and also the trajectories of Mercury and Venus, which are very roughly co-directional with it. If you are at the north pole, the equator is the horizon, and the planets’ travels south of the equator are below the horizon. Conversely as you move south, the horizon tilts down at its south end; in Ecuador or Uganda on the terrestrial equator, the celestial equator is vertical, and the planets’ sallies, too, are roughly vertical; for

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VULPECULA i y3

11

40m

May

Jun 1 w1

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30m

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21 Jun

Jul 1 11n

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VIRGO

+ 2˚ 2

b

i c

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i p

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i p

35m 30m

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u 10m

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Eu

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California Nebula

5m +20˚ +20

f

m ia

NGC1342

50m

k t

2 Oct1

globular cluster

e

21 +14˚ +14

4˚ +34

a ys

Aug

a

21

2 +32˚

13h

12h

11h

LEO

+10 +10˚

VIRGO

Nov

Nov

Sep Sep

Oct

N

21

Au 21 g 1

1 1Oct

y

1 Sep 11

-24˚

21 -26˚

x

o un 3 Jug A Aug

c t i l ip c e

20m

30m

May Jun r Ap Jul Jul ar M o n u b J e 3 Jan F

Jun

11

May 1

21

g

21

11

Feb 1

a

11

Apr 1

10m 9h 5m +20˚ +20

+18˚ +18

11 1 Mar

c t i +16˚ +16 p l i e c

+14˚ +14

y

CANCER a

Acubens Ac

x k

o to the ecliptic that it is nearer to being in the equato2 Pallas is in an odd orbit, so tilted rial plane. It was at the northernmost latitude of this orbit in Nov. 2010, and will be at the outermost point (aphelion) on Aug. 19, so when we pass it in July it is about at its most distant, high against the constellations of the northern Milky Way. 4 Vestaplies generally nearer in than the first three, and has a higher albedo (light color); surprising that it was not discovered first, and it is the only asteroid that, in most years, reaches theoretically naked-eye brightness. This year it is at its nearest (perihelion) in January, so almost its brightest (mag. 5.6) when we pass it in August, though low in Capricornus.

The next month 1 Ceres when we pass it is also well south (southernmost latitude from the ecliptic on Sep. 1) and approaching aphelion; it attains only to 2 magnitudes below Vesta, though that still makes it the second brightest of the year.

And 15 Eunomia, with its large size but the boring name Annibale De Gasparis gave it when he discovered it in 1851—a mere personification (Greek eu, “good,” and nomos, “law”) rather than a goddess. The asteroid is at perihelion in August, and at maximum latitude north of the ecliptic on July 26, so at opposition in November it is 3rd brightest of the year (actually equal 3rd along with 7 Iris) and 10h 9h well to the north in Perseus. sa +20˚ Ny Apr Mar +20 44ay M Feb CANCER Jan

Regulus

o2 o1

p2

+12˚ +12

+10˚ +10

For an interesting little chart of asteroid 16 Psyche (which was featured in Ast. Cal. 1999), see Jean Meeus’s Mathematical Astronomy Morsels IV, page 207. Psyche has a period close to 5 years; it has had a series of 5-yearly passes north of Aldebaran; the last was in Jan. 2006; in Jan. 2011 Psyche for the first time just misses having a conjunction with the star.

0˚

For more information about asteroids: The Minor Planet Bulletin of the Association of Lunar and Planetary Observers ($24/year US, Mexico, Canada, $34 elsewhere incl. air, add $1 if using credit card; from Derald Nye, 10385 E. Observatory Dr., Corona de Tucson, AZ 85641; 520-762-5504; nye@kw-obsv.org). Or the web-20˚ site of the Minor Planet Center: -20 http://cfa-www.harvard.edu/iau/mpc.html

-10˚ -10

Spica

-28˚

11

10h

Arcturus

Oct

+12˚ +12

Regulus

FINDER CHARTS on larger scale (0.75 cm per degree) for asteroids NGC1514 around the times of their oppositions. Position at 0h UT of each day (7 p.m. Eastern Standard Time of the previous day) is shown by a dot sized for brightness. The dots yare gray when the asteroid is in the morning sky, white in the evening sky (into which the asteroid passes at or near opposition). Stars are plotted from the Hipparcos catalogue. Projection is azimuthal-equidistant: angular directions and distances are true from the middle of the

0˚

44 n

z

right 15h ascension 14h

Dec

40m

LEO

+16˚ +16

MAPS showing paths of selected asteroids through the year. Ticks are at 1st of each month; arrowheads at end of year. Paths are thicker where asteroids are brighter; gray where they are less than 15° from the Sun.

SCORPIUS

10h

1 Jan

planetary nebula

galaxyf

declination

11

-22˚

Altair

x

NGC2903 21h

h

21

nebula

Coordinates of 2000

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a

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8 +38˚

11

open cluster

4

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11

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Dec a Nys 44

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1 Nov

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t

e

21h

Deneb

k

4 + 4˚

11

12h

ma g n i t u d e s

c

t

l c ee q u a t o r

0˚

i

e

6 + 6˚

e

ar M1

8 + 8˚

+16˚ +16

20h NGC6891 10m 1

20m

30m

c

21

11

+4 4˚

11

r Ap1

no s Ju

11h k

e

21

p

1120m

Pa lla s

h

-20˚ -20

b

1 CYGNUS

l Ju 1 1

40m

o + 8˚ 8

May 1

Co o r d i n a t e s o f 2 0 0 0 50m

12h

21 11 1 n u J 10m

0h

+18˚ +18

1 Au g

r

DELPHINUS

q -20˚ -20

NGC6879

e c l i 1 1 p t i cMay q

21

i

a

H20

21

+14˚ +14

M71

21

11

11

+16˚ +16

ay M1

11

2

11

Oct 1

CETUS

11

IC4997

21

g 21

v1 o 1 2 N

+20˚

g

1 21 Jul 1 1

-16˚ -16

21

21

Diphda

11

IC1305

NGC6886

h

DEELLP PH HIIN NU USS

1

AQIARIUS

-18˚ -18

b

NGC6905

+20˚

+18˚ +18

11

10m

VULPECULA

-14˚ -14

c De

21 1

20m

-12˚ -12

w2

galaxy WolfLundmark-Melotte

Se Denebola p

-16˚ -16

21

30m

NGC6830 NGC6820 19h39m Dumbbell 20h Nebula 50m +22˚

SAGITTA

May

1C ere s b

39m +22˚

23h28m

1 Jun

21

50m

11

-14˚ -14

11 Jul 1

21

1 Aug 1 1

-12˚ -12

0h

10m

20m

28m

59

Astronomical CalendarNGC 2011 6823

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Page 80

Astronomical Calendar 2011

Jan

Feb

Mar

-27

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

eclipse

-26

eclipse eclipse eclipse

-13

eclipse eclipse

-10 -9 -8 -7 -6 -5

Venus

-4

sup conj

-3 conj

-2

sup conj

ry sup conj rcu

-1

Me

0 +1

opp

Jupiter

sup conj

Me rcu ry Saturn

opp

conj

conj Saturn without rings

Mars

+2 +3 +4 +5 +6

+9

3 Juno

H ar

P1 00 9 C/2

2 Pallas

add Garr

3 Juno

n3 hman n-Wac ssman a w h opp c 73P S Pluto

y tle 2

+13

1 Ceres

G2 Hill C/2010

a

P

+12

006 P/2Levy T1

nomia 15 Eu

2 Pallas

e t s

3 10

+11

1 Ceres

s id o r

44 N ysa mia 15 Euno 2 Pallas

+10

+14

inf conj

opp

Neptune conj

Uranus

a 4 Vest

conj

+7 +8

opp

inf conj

inf conj

78P Gehrels

44 Nysa 2

conj

+15

Ho 45P Pajdnda-Mrk ušák osová

P

27

+20

P kos 45 r vá a-M ko nd šá in u el Ho jd m Pa om Cr

+19

n eli m m o Cr

P

06

P/20

+18

vy T1 Le

27

rels 2 78P Geh

+17

+23 +24 +25 +26

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

ite r Jup

Sa

Plu

to

tur n

s

Ur an us

x Po llu

Ne pt un e

150 o

Re gu lu

160 o

Feb

eclipse

eh ive

170 o

Jan

Be

180 o

90 o 80 o 70 o

Re Bee gu hi lus ve

ux Po ll

Ple iad es

100 o

60

An tar es

ica Sp

110 o

Ald eb ara n

130 o

Moon

western (morning sky)

140 o

120 o

rs Ma

o

50 o

Venu s

40 o 30 o

Me rc

eclipse

rn

s

Ju

50 o

Venu s

Plu to

r te pi

40 o

60 o 70 o

110 o

tar es An

Sp ica

Re gu lus

eh ive Be

ux Po ll

100 o

es

90 o

Ald eb ara n

80 o

Ple iad

120 o 130 o

180 o

o ut

eclipse

Pl

Ald eb ara n

170 o

rn tu a S

Ple

160 o

Ur an us

150 o

iad es

Ju p

ite

r

140 o

Ne ptu ne

eastern (evening sky)

eclipse

Sa tu

30 o

Ur an u

20 o

eclipse Sun

y ur erc M

10 o

Mars

eclipse

pt un e

0o

rcu ry

Ne

10 o

ur y

Me

20 o

12.9 6-inch (15-cm) 13.5 8-inch (20-cm) 14.4 12-inch (30-cm)

ELONGATION

comets

29P Schwassmann-Wachmann 1

+16

—is the astronomical way of measuring brightness. Each magnitude is roughly 2.5 times brighter than the one below it. (Magnitude 5 is exactly 100 times brighter than magnitude 10; etc.) This graph shows the apparent magnitude (that is, as seen from the Earth) of solar-system bodies.

The graphs of magnitude and elongation together show the best times of year to see each moving body. It is more easily seen (1) the brighter it is and (2) the farther it is from the direction of the Sun. In the magnitude graph, gray lines are used when a body’s elongation from the Sun is less than 15°.

Ticks on the Mercury and Venus curves mark superior conjunctions (upward ticks) and inferior conjunctions (downward) with the Sun. For other bodies they mark opposition (upward) and conjunction with the Sun (downward).

Superior planets (Mars outward) are brightest near opposition, but all planets brighten slightly (in Mercury’s case, a lot) at superior conjunction, because presenting their full faces toward us. This is in theory only, as we usually cannot see them past the Sun. Generally, planets other than Venus are on an upward slope of brightness when seen in the morning sky, a downward slope in the evening sky.

The curves are drawn thicker when the bodies are retrograding: in general this -1.4 Sirius is the time when Earth is closer to them. A dotted curve shows -0.7 Canopus ---naked-eye in daytime sky? the brightness of the ball of Saturn alone, without its brilliant 0.0 Arcturus, Vega, Capella rings (which, opening out since they were edge-on to us in 2009, are again contributing as much as half a magnitude).

1.4 Regulus The Moon at first and third quarter is not, as one might 2.1 Polaris suppose, half as bright as full (which would put it only 0.75 of 3.5 naked-eye limit, in cities a magnitude lower on the graph) but only about 1/11 as bright (2.6 magnitudes lower). See Ast. Companion, MOONLIGHT. 5 ----average conditions Asteroid names are precded by simple numbers, as in “1 Ceres”; “P” distinguishes periodic comets, “C” long-period 6.5 ----good conditions ones. Comets may behave unpredictably in brightness and follow quite different curves from those shown.

Magnitudes given are visual. Photographic magnitudes are 8.6 ----through blackened tube 9 2-inch binoc., 1-inch tel. about 0.7 to 0.9 greater (fainter); the peak sensitivity for traditional astronomical film is slightly blue-ward from that for the 10.5 2-inch (5-cm) telescope human eye. Magnitudes are calculated taking into account 11 Proxima Centauri 11.4 3-inch (8-cm) telescope phase-angle (the angle Sun-body-Earth; hence, the part of the body that is in shadow).

----fireballs------------------

Moo n

Moo n

-12 -11

MAGNITUDE

Dec

Sun

Try holding the page so that January is at the top and the planets moving downward. There are two ways to look at it: —Planets revolving around a star, as seen from one of those planets. The motion of Mercury and Venus resembles 19.5 200-inch (508-cm), visual the corkscrew motion of the satellites around Jupiter. But the other planets slip always backward, because, being farther out than us, they are losing the race with us around the Sun. The 23.5 ----photographic Moon, searing repeatedly across the foreground, describes a kind of time-cylinder around us.

(28) faintest objects —Imagine the diagram cut in half along the Sun-line, and photographed (31) faintest objects recorded put back the other way around: 0° (the Sun-line) at left and with Hubble Space Tel. right, and 180° down the center. The Sun-line now represents the dawn horizon (on the left) and the sunset horizon (on the right). The line down the new middle (180°) is the meridian at midnight; the graph has become a graph of the night sky’s whole expanse, from sunset to sunrise. On the new right, the superior planets (including, this year, Mars) sink into the sunset horizon; Mercury bobs up into view from it three times; Venus, in the later part of the year, climbs slowly from it; the young Moon leaps repeatedly out of it. In the new middle, the superior planets (except, this year, Mars) are shown crossing the midnight meridian at their oppositions, when they are brightest. On the new left, the dawn horizon, the superior planets emerge from their conjunctions with the Sun; Mercury keeps bobbing out on this side also; Venus sinks slowly; and the waning Moon dives repeatedly.

The crossing of any two lines represents a conjunction. A planet is at conjunction with the Sun if it crosses the 0° line, and at opposition if it crosses the 180° line. At 90° east or west of the Sun, a planet is at east or west quadrature.

The Moon is new when it crosses 0°; full at 180°; at first and last quarter when it is 90° east or west. It is at conjunction with planets when it crosses their lines. The diagram reveals the times when the Moon fills the midnight, morning or evening sky with glare, and times when its narrow crescent (near to the Sun) joins groupings of planets.

The greatest elongation Venus reaches can vary between about 45.4° and 47.3°. This year it reaches 47.0° west. The greatest for Mercury varies between 17.87° and 27.83°; this year it reaches —23.3°, 18.6°, —26.6°, 26.8°, —18.1°, 22.7°, —21.8° (negative meaning westward). The asymmetry of its swings is caused by its elliptical orbit: if at one elongation it is at perihelion, at the next it will be near (not at) aphelion. For north-hemisphere observers it is not usually highest above the horizon when at the larger maxima of elongations; see the MERCURY section.

Elongation really means angular distance measured from the Sun in any direction, not just along the ecliptic (difference in longitude). Even at conjunction, a planet is usually a little north or south of the Sun; at opposition it is north or south of the anti-Sun point.

Therefore elongation doesn’t exactly reach 0° or 180°; instead, the lines on the graph curl away a little before reaching these limits, then after a jump resume on the other side. This is noticeable for Pluto, which still lies about 4° north of the ecliptic, and so cannot have elongation less than 4° or more than 176°; also for Venus and Mercury at inferior conjunctions where they pass well north or south of the Sun. Stars too can be said to have elongation from the Sun. Shown are the five bright stars and two star-clusters (Pleiades and Beehive or Praesepe) near the ecliptic, often seen in conjunctions with the Moon and planets. They serve to relate the rest of this time-diagram to the spatial background of the sky. Lines for stars north and south of the ecliptic would curl away; a star at the ecliptic pole always has elongation 90°.

The graph strictly shows the bodies’ angular relations to the Sun, not to each other.

Yet it serves to reveal times when they move side by side or in contrary directions, leave large parts of the sky bare, or gather in knots (visited fleetingly by the Moon).

On the Virgo side of the sky is Saturn; on the opposite Pisces side are the three other outer planets, Jupiter having overtaken Neptune in September 2009 and Uranus in September 2010. In front of these three circles Mars, which last passed Saturn in Aug. 2010 and next passes it in Aug. 2012; and across foreground of all of these we see Venus and Mercury twirling around the Sun.

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Astronomical Calendar 2011

81

Contents 2 calendar and Julian dates 3 Explanations 6–29

MONTH BY MONTH

30 Highlights of the Year Sun and Seasons 31 The Moon 33 Special Moons 34 Young Moon, Old Moon 36 Dark of the Moon Strip-Chart of the Moon 37 Corrigenda 38 Eclipses

by Joe Rao 40 CENTERFOLD MAPS 42 46 50 51 52 53 54 55 56 57 58 60 66 68 69 72 [The graph is constructed for the northern hemisphere, but when the substitutions in brackets are made it also serves—approximately—for the southern hemisphere.]

Recognize Polaris by the surrounding star-field. Then align your telescope’s axis with the celestial pole.

CEPHEUS URSA MINOR

QUICK REFERENCE

74 76 79 80 81 82

Eclipses, continued Mercury and Venus Mars Outer Planets Jupiter Satellites of Jupiter and Saturn Saturn Exoplanets (bonus page) Uranus and Neptune Pluto Asteroids Comets

by Alan Hale Occultations

by Richard Nugent Conjunctions Meteors

by Alastair McBeath Deep-Sky Profiles

by Fred Schaaf Light Pollution

by Fred Schaaf Spaceflight

by Clifford Cunningham Glossary Magnitude, Elongation Quick Reference Rising and Setting

Fill this in as your Personal Reminder: Example:

the Engagement Ring

66 hh on

o eM

2150

2100

t ren

eo

siz

pa

ap

2050

2000

cle

cir

4˚

1/

1950 1900 1850 North Celestial Pole moving by precession

1188 hh

Bright Stars. After aligning your telescope’s axis with the celestial pole (and switching on the clock-drive if any), point the telescope at one of these easily found stars. Then turn the right-ascension setting-circle to the right ascension given. This will set the telescope to sidereal time. You can then point it at any other object by looking up the object’s coordinates (epoch 2000) and turning the setting-circle to them. Declination is given as a check: if, when you point the telescope at the star, the declination setting-circle reads wrongly by more than a degree, you did not align closely on the pole.

(2000) R.A. dec. mag.

Hamal (α Ari) 2 h 10.2m +23 ° 28´ 2.0 Aldebaran (α Tau) 4 35.9 +16 31 0.9 Rigel (β Ori) 5 14.5 — 8 12 0.1 Capella (α Aur) 5 16.7 +46 00 0.1 Betelgeuse (α Ori) 5 55.2 + 7 23 0.5 Sirius (α CMa) 6 45.1 —16 43 —1.5 Procyon (α CMi) 7 39.3 + 5 14 0.4 Pollux (β Gem) 7 45.3 +28 02 1.1 Regulus (α Leo) 10 08.4 +11 58 1.4 Spica (α Vir) 13 25.2 —11 10 1.0 Arcturus (α Boo) 14 15.7 +19 11 —0.0 Antares (α Sco) 16 29.4 —26 26 1.0 Vega (α Lyr) 18 37.0 +38 47 0.0 Altair (α Aql) 19 50.8 + 8 52 0.8 Deneb (α Cyg) 20 41.4 +45 17 1.3 Markab (α Peg) 23 04.8 +15 12 2.5

t sa

ls

va

er int

1122 hh

2nd mag bright . 6.5 est s tar,

00 hh

2200

f th

++9900 oo

7 8 9 10

++ 88 99 oo

2250

6

declina ++ 88 99 otoion

ma g n i t u d e s

Polaris α Ursae Minoris mag. 2.1

Name of place:

__________________

Traveler’s Rest, S.C.

Elevation:

______

1,100 feet

Latitude:

______

35° N

Longitude:

______

82° 30´ W

Standard Time Zone: Standard meridian of time zone: Universal Time or Greenwich Mean Time: Daylight-Saving Time at above UT: Standard Time at above UT: Local mean time at above UT:

______

Eastern

______

75° W

12h UT

12h UT

______

8 am EDT [Standard Time + 1]

______

7 am EST [UT — (75° / 15)]

______

6:30 am [UT — (82.5° / 15), or Standard Time — (7.5° / 15)]

Time-zones. To convert Universal Time to standard time, add the number (if it is negative, subtract it). Then for so-called daylight-saving (summer) time, where used, add 1. If result is negative, add 24; date is previous day. If result is over 24, subtract 24; date is next day.

Page 82

l

R

re

e

Q A

d si

f

o

rs

Europe

U.S.A.

ris ut o Pl

ets

s

s Sa tu rn s

ise

ise

ris e rn tu Sa

rr

0

1

rn se ts

rises

es

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0

1

l

A T

t se

e

N

11

IN M

G

8

re

11

R

rs

21

N

s

f

L 1

C

Neptune opposition

e

O

1

E

id

E

21

E

Perseids

ti

1

I

a

21

Sun transits

6

u pt

Mars

pit er

ris

es

Ju

Ur

Sa tu

ris us

N

an

ite r Jup

Mars sets

s set

5 p.m. clock time (summer)

ep

Pl

ne

21

U

s

es

e

n tu

se

U

R

ris

Sun transits

ts

ry cu

C

11

er

N

A

s

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21

4

M

C

Pluto opposition

ets

E

8

IE

R

A

11

S

o ut

ets Venus s

R

ys

G 1

ur

E

erc

M

M

IN

21

S

1

1

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o

h

I

Eta Aquarids

ts

u

6

2

se

es

e ris

Pl

Sa

o

rs

o ut

tu

f

rn

d

si

s

ris

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21

P

us

a

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C

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Lyrids

Ur an

l

S

E

omica l twilig ht nautic al twil ig h t civil tw il SUN R ight ISES

m

4

U

June

21

U Q A

astron

March

Sun transits

S

IE

S

July

11

S

11

2

A T

August

1

2

R

A

Saturn opposition

11

21

2

P

C

light al twi omic astron light i cal tw nauti t wiligh civil t SETS SUN

April

P

21

1

N

R O IC

ts

IS

e

21

11

S

U

IU

R

11

1

R

A

11

0

A

1

May

ates

n rises

21

2

se

S

E

C

21

11

last-quarter Moo

full Moon sets last-quart er Moon culmina tes new Mo on rises

11

y

0

11

sets

full Moon culmin

full Moon rises

u

1

n Jup us s ite ets rs ets

lminates

o

21

first-quarter Moon

first-quarter Moon cu

h

11

s

un es ets pt new Moon sets

r cu er M

1

ti

a

A

U

21

Ur a

m

IU

2

5 p.m. clock time

e

S

2

Ne

se ts Plu to

January February

1

ises

Venus sets

C

A

ry r rcu Me

R

P

21

rises

O IC

s Venu

R

2

11

Mars sets

N

0

11

s

19

ite

18

er

17

ise

16

Ju p

15

S

U

pt un

14

sr

13

1

an u

local mean time

12

Ur

This hourglass shows times when the Sun, Moon, and planets rise and set, for latitude 40° north, longitude 0°. (They differ little for other longitudes, much more for other latitudes.)

These are local mean times; to adjust them to your clock time, see the “Personal Reminder” on the preceding page.

The lines representing days (actually drawn only for days 1, 6, 11, 16, 21, 26 of each month) begin at midnight, which is in the middle because we choose to show night rather than day undivided. Each day-line ends at the point where the next day starts, so there is really just one time-line, a cut and flattened helix.

the times of sunset and sunrise would be if the diagram were plotted to apparent (true solar or sundial time, in which days vary slightly in length) instead of mean time. Again, the difference is the “equation of time.”

At a planet’s opposition it is up all night (roughly) and none of the day.

Major meteor showes are marked at the local times when their radiants are highest.

Two thick vertical lines displaced to the left in summer represent 5 p.m. and 8 a.m. by the clock (for places on the meridian of their time zone). This shows how the purpose of setting clocks back from standard to “daylight-saving” time is to approximate to the earlier rising of the Sun. In summer we call the true 7 o’clock “8,” the true 12 “1,” etc.

12 3 4 5 6 7 8 9 10 11 1 Quadrantids

es

RISING AND SETTING

The dark zone down the middle is night, between the curves of sunset and sunrise. The three bordering gray bands are the times of civil, nautical, and astronomical twilight, which are defined as being when the Sun is less than 6°, 12°, and 18° below the horizon.

Slanting lines show the hours of sidereal time: that is, which hour of right ascension is on the meridian. Thus 0h-1h sidereal time is the “Andromeda Hour,” when that gore of the sky is highest. Sidereal hours are 10 seconds shorter than clock (solar) hours and thus fall 4 minutes earlier each day.

The times of the Sun’s transit across the meridian are shown by orange spots. This time differs from mean noon by the amount called the “equation of time” (see the GLOSSARY). Orange curves show where 1 2 0 20 21 22 23

Ne

Astronomical Calendar 2011

8 a.m. clock time (summer)

82

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Mars 8 a.m. clock time ris

10/20/2010

es

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C

A

0

1

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1

11

h 2 1

11

O

E

O

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L

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16

17

20

21

23

us

0

4

5

6

7

8

1

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pt

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6

9

10

11

S

IU

P

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Ma rs

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3

11

21

IB

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2

1

L

Ursids

1

A

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4

1

ts

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rise

ris

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19

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8 a.m. clock time

ise s nr tu r Sa 18

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Ur an

Ma rs r

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12

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Geminids

ets

Europe

U.S.A.

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21

s se

Ur

1

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sr

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es

u

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p Ju

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es

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Leonids

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21

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December

l

a

P

Sa tu

IU

1

ti

21

IR

1

u Ven

November

e m

S

6

V

Jupiter opposition

Mercury sets

L 1

11

G

Orionids

A

Ne pt

R

IB

1

1

O

21

11

2

4

1

5 p.m. clock time

October

1

11

21

Uranus opposition

Sun transits

September

u

o

11

1

21

8 1

12