South Canterbury Astronomers Group Newsletter

South Canterbury Astronomers Group Newsletter Volume One – Issue Twelve

April 2010

Next meeting – Friday 30th April 2010, 7-15PM at G-Block, Aoraki Polytechnic.

Programme includes, Cleaning Telescope Optics, Aligning Telescopes, Recent Solar activity & Aurora, a report on recent Canterbury University astronomy camp.

S.C.A.G Contact Information

S.C.A.G Membership Information:

South Canterbury Astronomers Group c/- The Secretary 28 Kiwi Drive Timaru, 7910 New Zealand Ph 03-6883735

Membership types:   

Ordinary member – anybody may apply Associate member - Full time students & Snr citzens Family membership – Up to two caregivers and dependant children.

Website: www.scastro.co.cc Website sponsor: www.nztelescopes.co.nz

S.C.A.G Meetings: Monthly meetings are held last Friday of each month, starting at 7-15PM, at G-Block Aoraki Polytechnic Timaru. Meetings begin with 15 minutes chat time, followed by the evenings programme.

Monthly meetings consist of Astronomy news, guest speakers, practical demonstrations, equipment discussions, what’s in the night sky and more.

The meeting room is a modern facility with multimedia equipment available, warm and very comfortable, outside areas for observing, especially in the winter months.

Observing sessions: Every month we hold at least one observing sessions for members at one of our dark sites.

Public sessions are also held as required.

Visit our website to keep up to date.

S.C.A.G Steering Committee: President - Russell Colina Ph 6860475 Secretary - Robert McTague Ph 6883735 Treasuer - Gary Prouting Ph 6843800 Committee- Janet Russell Ph 6861372

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Ordinary Associate Family

$40.00 $20.00 $60.00

Contributions to this newsletter are welcome, deadline is the first Friday of each month, includes articles, observing notes and equipment for sale. Please send to the Secretary, email langwood@xtra.co.nz

Please Note: The content of the newsletter is for general purposes only, not necessarily the official opinion of SCAG. SCAG reserves’ the right to alter content as required.

Please ask if you have questions regarding content.

Up coming events: 

Friday 23 April, from 7pm – Public Star Party at Geraldine township. South Canterbury Astronomy Group will be available with telescopes to let the public view the night sky. Location corner of Hislop St and Cox St Geraldine.

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Saturday 24 April, from 7pm – Public Star Party at South St Reserve. Open to everybody, your chance to look at the night sky through a range of telescopes. This is a real dark site, you will see a lot of detail! South Street reserve is located behind the Caledonian grounds Timaru.

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April 30th, 7-15Pm monthly meeting at Aoraki Polytechnic. Programme includes, Cleaning Telescope Optics, Aligning Telescopes, Recent Solar activity & Aurora, a report on recent Canterbury University astronomy camp.

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May observing session for members , location and date to be advised.

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May 21st 7-15PM our monthly meeting for May is being brought forward because of the Dunedin conference. This will also be our first AGM (short and sweet) if you would like to help as a committee member please contact Russell , Gary, Janet or Robert, we need more help please.

We will hopefully have an international speaker joining us via internet conference call, more details about this soon. You will have the opportunity to put questions to our speaker.

Matthew has kindly put arrangements in place with Aoraki Polytechnic to make this happen.

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Friday May 28th to Sunday 30th May: Royal Astronomical Society of NZ National Conference in Dunedin. Visit http://www.rasnz.org.nz for more details, or contact Robert (6883735) for more details. I am pleased to advise that www.nztelescopes.co.nz is one of the conference major sponsors.

No answers supplied, it should be very easy.

Mt John Observatory – A short History Sourced from http://www.teara.govt.nz

New Zealand was slow to embrace astrophysics – the branch of astronomy that seeks to understand the nature and properties of stars and associated objects in space. It was not until the Mt John Observatory was established that such research was undertaken in New Zealand.

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Foundation Mt John Observatory is a high-tech research observatory, founded in 1965 as a joint project between the universities of Pennsylvania and Canterbury. It is at Lake Tekapo, in the centre of New Zealand’s South Island – where there is the greatest chance of dark, clear skies.

Equipment The first major instruments to be installed were three telescopes for sky photography. They were used in the late 1960s to produce a photographic map of the southern sky, known as the Canterbury sky atlas.

In 1970 and again in 1975, 60-centimetre Cassegrain telescopes were installed. One is used for photometry (the measurement of light intensity), mainly of variable stars (stars that vary in brightness).

The other is dedicated to observations of gravitational microlensing.

The McLellan telescope A large 1-metre Dall-Kirkham Cassegrain telescope was installed at Mt John in 1986. Known as the McLellan telescope, it is used mainly for high-resolution spectroscopy of stars with a Hercules vacuum echelle spectrograph (spectroscopy is the study of the way atoms absorb and emit electromagnetic radiation). The data can be used to measure star velocities, temperatures, pressures, chemical composition, rotation rates and other parameters.

The MOA project MOA stands for microlensing observations in astrophysics. Microlensing is caused by the bending of light rays by the gravitational field of a massive object (the lens), with the result that the light from a distant star can be amplified in brightness, typically for 3–5 weeks.

The MOA project began at Mt John in 1995, mainly supported by Auckland, Canterbury and Victoria universities in New Zealand and Nagoya University in Japan, for detecting and observing microlensing events. Fifty or so events are discovered annually by astronomers at Mt John. In 2003 MOA researchers discovered a planet orbiting a distant star, the first such occurrence to have been detected with microlensing techniques. The subsequent discovery of a large planet in 2005 by a collaborative group of astronomers, including MOA researchers and two Auckland amateur astronomers, confirmed the value of microlensing for planet hunters.

New Zealand’s largest telescope A fourth reflecting telescope, constructed in Japan, was installed at Mt John in late 2004. It has a 1.8metre aperture and a large electronic camera mounted at the prime focus. This telescope, New Zealand’s largest, is used for photometry as part of the MOA project, and is the largest telescope in the world dedicated to microlensing.

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Alan Gilmore Alan Gilmore has been resident superintendent of the Mt John Observatory at Lake Tekapo since 1996. An amateur astronomer since his school days, he began professional astronomy at the Carter Observatory, Wellington, in 1970.

Alan is involved in many observing programmes at Mt John, including, with wife Pam Kilmartin, a long running programme to track near Earth asteroids

Pam Kilmarton

Pam has discovered some forty asteroids, each one in collaboration with Alan, both of them are also active comet-hunters.

She is a Fellow of the Royal Astronomical Society of New Zealand (RASNZ).

Alan and Pam have lived and worked at the hilltop observatory since 1980

Alan Gilmore & Pam Kilmarton (Life Membership to SCAG) Alan Gilmore (Patron of SCAG) At our November 2009 meeting the proposal was put forward to offer Alan Gilmore of Canterbury University’s Mount John Observatory the title of Patron to our group. And to also offer Alan and wife Pam a lifetime membership to our group in recognition of the significant assistance that they have provided to our group.

This proposal was unanimously accepted by members at this meeting and a letter was drafted and sent from our president Russell Colina to Alan and Pam making this offer to them.

The committee of the South Canterbury Astronomers Group is pleased to announce to our members that Alan has accepted our offer and we can now officially name Alan Gilmore as Patron of the South Canterbury Astronomers Group.

Also Alan and Pam have accepted our nomination for lifetime membership to our group and we are pleased to accept a donation of $100.00 from Alan and Pam. This is great news and an honour for our group to have persons as highly qualified as Alan and Pam involved with our group. We look forward to a long association with Alan and Pam and warmly welcome them to our group.

Russell Colina President.

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Web Cam Astro Imaging Due to a donation SCAG now has a Philips ToUcam Pro II Astro webcam that can be loaned out to members.

This camera is recognized as the best entry level webcam available to start in Astro imaging.. Not made anymore but widely sought after by astronomers worldwide, we are very lucky.

Those members that attended the meeting a few months ago about Astro imaging, went home with a CD that included a tutorial about imaging by Damien Peach, this camera is the camera recommended in that tutorial. http://www.damianpeach.com/

The kit includes that nose cone, ready to slip into the eyepiece holder on any telescope with a 1.25 inch focuser.

A CD with the software required, and USB cable.

Will run on Windows XP, and Vista computer operating systems.

The camera kit can be loaned out to members for a month at a time.

If need be, training can also be provided. Please ask.

These images taken using the camera on a basic telescope setup.

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How To Collimate Your Newtonian Reflector & Dobsonian Telescope

by Nils Olof Carlin for Sky & telescope.

One of the most frequently noted disadvantages attributed to the Newtonian reflector is its need for regular collimation. However, this supposed disadvantage can be reduced to a minor task if lining up the optical elements is approached logically and methodically.

S&T / Craig Michael Utter Suppose you have bought a fine guitar with a lovely sound and are learning to play it. But after a while, you notice that it has gone slightly out of tune. What do you do? Learn how to tune it, or trade it in for a piano?

Your Newtonian reflector will give great images of stars and planets — but only as long as you keep it well tuned. The "tuning" of a telescope is known as collimation. You may have heard that it is incomprehensible, tedious, time-consuming, a pain in the neck, and best avoided. I hope to convince you that it is none of these things. You can master it and in only a minute or two get your instrument ready for a star performance.

Know Your Telescope

This diagram illustrates the Newtonian reflector's optical components and some of the structures that support them.

Aligning and centering these components is necessary for optimal optical performance.

S&T illustration If you aren't already acquainted with the optical parts of your telescope, now is the time. Here are the components that you will be lining up: The primary mirror. This is the paraboloidal mirror at the bottom of the tube. It has an aluminized surface that reflects starlight to form an image at the focal plane. The important thing to know that it has an axis of symmetry — the optical axis. On this axis, at the focal point, is a "sweet spot" where images of stars and planets are as sharp and crisp as 8

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9 they can be. Outside the sweet spot, an aberration known as coma visibly degrades the image. Coma makes stars appear asymmetric even if the telescope is perfectly focused — the farther the star is from the center of the focal plane, the worse it gets. In particular, this aberration can dramatically reduce the clarity of planetary detail.

Surprisingly, the size of the "sweet spot" depends only on the main mirror's focal ratio (the mirror's focal length divided by its diameter) and not its size. For instance, even a perfect f/4.5 mirror, small or large, can provide "diffraction limited" performance only within a 2-millimeter (0.08-inch) circle at the focal plane. An f/10 paraboloid's sweet spot, by contrast, spans 22 mm (0.87 inch). (For the mathematically inclinded, the sweet spot's diameter is proportional to the cube of the f/ratio.)

The aberration known as coma is enemy number one for Newtonian reflectors — even a perfectly made mirror suffers from it. Shown in these simulated star images (from left to right): a star at focus and centered in the eyepiece (images are coma free), halfway to the edge of the sweet spot (coma will have no visible effect), at the edge of the sweet spot (coma begins to have an effect), at twice the radius of the sweet spot, and four times the radius of the sweet spot.

Nils Olaf Carlin The primary mirror is held in an adjustable cell designed to support the mirror without deforming it. By adjusting the cell's collimation screws we can fine-tune the mirror's tilt and accurately position the sweet spot where we want it. Because the sweet spot can be very small, this is by far the most critical part of collimation. Have a look at your telescope and make sure you know where these adjustment screws are and how they work.

Accurately placing the primary mirror's center dot is an important precursor to accurate collimation. The dot (black electrical tape) is temporarily affixed to the underside of a pair of flexible, transparent rulers mated at right angles to one another. Once the rulers are correctly positioned (with the dot equidistant from the mirror's edge in all four directions), bend them down to attach the tape spot to the mirror.

S&T / Craig Michael Utter To make collimation easy, the center of the mirror should be marked in some way. I recommend marking it with a piece of electrician's tape. Don't make it too small — a ½-inch-diameter (or even slightly larger) spot works well. As long as it is smaller than your diagonal mirror, it will not affect your telescope's performance. If you plan to use a laser collimator, make a hole in the center of your spot. (Another approach is to use an adhesive binder reinforcement ring, the kind used by generations of school children to keep their homework from flying out of their 3-ring binders.)

The secondary mirror. This is a small, flat mirror that serves to move the image formed by the primary to the side of the tube, where it is viewed with an eyepiece. To minimize harmful diffraction effects, the secondary, or diagonal, mirror is generally only large enough to let the central portion of the focal plane 9

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10 receive light from the whole primary mirror. You should center this fully illuminated area in the eyepiece by positioning the secondary in the correct location.

The secondary is attached to an adjustable holder suspended on a spider — often a cross made from thin sheet metal. Identify the adjustment screws for the secondary holder and the spider.

The eyepiece.

One of the first steps in collimating your reflector is to identify the various components as seen from the focuser. Owing to the multiple reflections, this can seem harder than it really is.

Sky & Telescope illustration The third optical component in the telescope system is the eyepiece. It is a complex magnifying lens used to view the image formed at the focal plane. Like the primary mirror, the eyepiece has an optical axis, and this axis should be aimed at the center of the main mirror for best performance — though in practice it is the center axis of the focuser drawtube that you aim at the primary mirror.

A good eyepiece will render a sharp image in the central parts of the field of view (its sweet spot), but toward the edge not even the best and most expensive eyepieces can produce a perfect image. For this reason it is important to make sure that the sweet spots of the primary mirror and the eyepiece match up — the ultimate goal of collimation.

Now that you know what you're dealing with, look into the empty focuser and try to identify the optical parts just described. This is best done during daylight, with the telescope aimed at the ceiling or the sky (be careful to avoid the Sun). The illustration to the right shows what you should see: the secondary mirror in its holder, its elliptical face tilted 45° and appearing circular. With your eye close to the focuser, you can see the primary mirror reflected in the secondary, and the secondary and its spider in turn reflected in the primary. Finally, inside this reflection of the secondary, you can see the focuser drawtube and your eye.

Three Steps to Collimation

While looking through your collimating eyepiece down your Newtonian reflector's focuser tube, follow these three steps to collimate your reflector. The steps are simple in principle. However, depending on how your telescope is built, you may require a great deal of dexterity — or a partner (especially if your 10

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11 telescope is large) — to manipulate your optics; collimation adjustments are much more easily made with some instruments than others.

S&T illustration Once you are acquainted with the telescope's optical parts and what they look like in the focuser, you're ready to proceed. To get your telescope well collimated, here is what you need to accomplish:  Step 1: Center the secondary mirror on the axis of the focuser drawtube.  Step 2: Aim the eyepiece at the center of the primary mirror.  Step 3: Center your primary mirror's sweet spot in the eyepiece's field of view.

In most cases, only the last of these three steps will need to be repeated regularly; the first two are more or less set-and-forget operations. Now let's get to the nuts and bolts of actually collimating your reflector.

Step 1:

Positioning the secondary mirror can be made much easier if a piece of cardboard is placed between it and the primary mirror.

This eliminates the confusing reflections coming from the primary mirror.

S&T / Craig Michael Utter Begin by making sure that the focuser and the secondary are lined up. The simplest and best tool for this step is a sight tube.

(Read our sidebar for more on this collimation tool and others.)

You slide it into the focuser, as you would an eyepiece, and look through the tube's peephole at the secondary. (If the secondary is far out of adjustment, you should first tilt and/or rotate it to get the reflection of the spot on the primary roughly centered in the sight tube before you proceed.) It may be difficult to distinguish the edge of the secondary from the reflected edge of the main mirror, so place a piece of white cardboard between the secondary mirror and the primary, as shown here.

The elliptical secondary should appear round and well centered in the circular opening of the sight tube. If it is, Step 1 is done. If not, either the secondary holder or the focuser (or both) needs attention.

Try adjusting the secondary holder first. You can usually move it toward or away from the primary by adjusting the center bolt that joins the holder to the spider.

If the error is toward either side of the sight tube (90° to the optical axis), also check to find out if the secondary is well centered in the telescope tube. If it isn't, adjust the spider's mounting screws until it is. If this checks out fine, then tilt the focuser by putting shims under its mounting plate.

Step 2: Here you adjust the tilt of the secondary mirror to aim the focuser's axis at the center of the primary. First, remove the cardboard from the spider. Now, while viewing through the sight tube, carefully adjust the screws that tilt and rotate the secondary until the primary mirror's reflection appears centered in your field of view. If your sight tube has cross hairs, align the primary's center spot with them; otherwise, center the outer edge of the primary within the sight tube. (Make sure that the sight tube is racked in far enough to let you see the whole primary mirror.) A laser collimator is even better for this step — just center the laser beam on the primary's center spot.

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12 Described in Sky & Telescope's December 2001 issue, Gary Seronik's 8-inch travelscope features several innovations, among them a wooden secondary-mirror support that allows the secondary mirror's collimation to be easily adjusted by hand, without the tiny, hard-to-manipulate screws common to commercial units.

S&T / Craig Michael Utter A small error in secondary alignment is usually not a problem. As long as the pointing error is no more than 1 or 2 percent of the main mirror's diameter, it makes no visible difference. However, if you plan to use a laser collimator in Step 3, you should be aware that even a tiny misadjustment here will throw off the final collimation.

If you have a truss-tube telescope, you will need to repeat Step 2 each time you reassemble the scope. With a solid-tube reflector, you need only check this once in a while.

Step 3: In this, the final and most critical step, you need to tilt the main mirror to center its sweet spot (and its optical axis) in the focuser. This procedure should be done at the beginning of each observing session and checked occasionally during the night, since temperature changes or routine handling may cause your telescope's components to shift enough to change collimation.

The best tool for this procedure is a Cheshire eyepiece or laser collimator. Put it in the focuser and observe the reflection of its shiny 45°-angle face in the primary. By turning the primary's adjustment screws you can move this reflection until it appears centered on the primary mirror's center spot. If you can make these adjustments while looking in the Cheshire, so much the better; otherwise an assistant can be very helpful. Most mirror cells have three adjustment screws or three pairs of push-pull adjustments.

For simplicity's sake, I recommend using only two of the adjustments — the third one (which might as well be the one that is hardest to reach) can be left alone unless you run out of adjustment on one of the others.

When Step 3 is done, the optical axis is accurately centered in the focuser, and collimation is complete.

However, if you look carefully you will notice that the Cheshire eyepiece does not appear exactly centered inside the shadow of the secondary. Don't worry; this is in fact how things should look because the secondary mirror is slightly offset. (For more on the subject of secondary offsets, go to this sidebar.

But bear in mind that you needn't master the somewhat elliptical reasoning behind the subject in order to collimate your telescope well!)

A laser collimator is often used for Step 3, by centering the returning beam on the laser's faceplate.

However, this method has problems that belie the laser's presumed accuracy. Why? Suppose that in Step 2 the laser beam has missed the true center of the primary mirror by a small distance, for example, 2 mm.

Even if the primary mirror happens to be exactly collimated (its center precisely aligned with the center of the eyepiece), the returning laser beam will be parallel to the main mirror's axis but will miss the center of the laser faceplate by 2 mm. If you then tilt the main mirror to center the beam returning to the laser, the collimation will be 1 mm off! Unintentionally, you will have caused a miscollimation great enough to affect the performance of a short-focal-length telescope. This extreme sensitivity to a small and otherwise unimportant error in Step 2 is the Achilles' heel of the laser collimator. So even if you use one for rough alignment in Step 3, it is better to use a Cheshire eyepiece for the final adjustment.

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Star-Testing Your Collimation

Is your telescope only slightly out of collimation? An out-of-focus star is all that is needed to fine-tune collimation. If the shadow of the secondary mirror is slightly offset (left), the scope could use adjustment. Find the location of the collimated field — the part of the focal plane where the out-of-focus star is symmetric — and adjust the primary mirror's collimation to bring the collimated field into the center of your eyepiece's field of view.

Sky & Telescope Once your telescope has cooled down and is well collimated, it should be ready to perform at its best. At high magnification (25× to 50× per inch of aperture, or 1× to 2× per mm of aperture) and in good seeing conditions, stars at focus should appear in the eyepiece as tight, symmetric diffraction disks. However, if stars at the center of the field show the telltale asymmetry of coma, double-check your collimation with the Cheshire eyepiece. If the center spot still looks centered, then it isn't located at the primary's true optical center.

Nils Olof Carlin is seen here with his homebuilt portable 13.1-inch (33-cm) truss-tube Dobsonian reflector. Starting with only the primary mirror, this telescope was Carlin's first telescope-making project — although it has been modified many times.

Nils Olaf Carlin If this is the case with your mirror's center spot, ignore it for now and try tweaking the primary's collimation, in small steps, until you have centered the best image in the field of view. (This method was described in detail in the June 2001 issue of Sky & Telescope, page 125, and is illustrated below.)

The Cheshire will now indicate the location of the primary mirror's true optical center. If necessary, move the spot to the correct position or put another, larger piece of tape on top of it.

If you know that your primary mirror spot is okay (and in most cases it will be, if carefully centered), there is no need to routinely fine-tune your collimation with a star test — the Cheshire eyepiece is not only easier to use, but it is more accurate if the seeing is less than ideal, which it is most nights.

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14 Now your telescope is in perfect tune, and the improvement in performance should be obvious. If not, try to deliberately miscollimate the primary, and see what it does to a high-magnification view of a planet. After this demonstration, you'll never let your scope go out of collimation again.

If you need help collimating then make contact with Robert McTague, he has a laser collimator that can be used to collimate your reflector telescope.

The Solar System in May – compiled by Brian Loader (RASNZ) -------------------------The usual notes on the visibility of the Planets for May 2010 have been placed on the RASNZ web site: http://www.rasnz.org.nz/SolarSys/May_10.htm.

THE PLANETS IN MAY Mars and Saturn remain visible as evening objects during May. Mars will set late evening, Saturn in the early morning hours. Venus will be prominent but low to the northwest for a while following sunset early evening.

Jupiter will be an obvious morning object to the northeast, closing in on Uranus during the month. Mercury will be lower in the morning sky, but should be readily visible in the second part of the month.

THE EVENING SKY VENUS will move a little higher into the evening sky during May, setting 2 hours after the Sun by the end of the month. It starts the month in Taurus, below Aldebaran. During May Venus will move across Taurus below Orion and into Gemini on May 20. By the end of May, Venus will be about 11 degrees from Pollux.

MARS sets shortly before midnight for most of NZ at the beginning of May and 45 minutes earlier by the month's end. Transit will be about an hour after sunset, making early evening the best time for observation. During May Mars will continue to fade a little, from magnitude 0.7 to 1.1, as the Earth moves further away from it.

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15 By the end of May, Mars will be 3.5 degrees from Regulus, the star just a little fainter than the planet.

Also Vesta, at magnitude 7.7 visible in binoculars, will be 7.5 degrees from Mars.

Mars starts May in Cancer and moves into Leo on May 13. On the 20th the 42% lit moon will be 4 degrees from Mars, closest about 8 pm, with the moon to the upper left of the planet.

SATURN remains the best placed planet for evening viewing during May. It transits close to 10 pm on May 1 and 2 hours earlier at the end of the month. The planet will be only just north of the celestial equator so is at a moderate altitude as seen from NZ and considerably higher than Mars.

Saturn will be in Virgo, about 25 degrees from Spica, alpha Vir. Saturn will be to the lower left of the star when the planet is highest. Saturn will be far closer to beta Vir, magnitude 3.6, the two being about 2 degrees apart during May. The closest approach of the moon to Saturn during May will be on the 10th, when the 75% lit moon will be about 8 degrees from the planet in the early evening.

Saturn's rings are still only open a slight amount and in fact close slightly during the month as the Earth moves ahead of Saturn. They will appear as a bright bar either side of the planet in a small telescope.

Quite high magnification is needed to see them as rings.

THE MORNING SKY

JUPITER rises soon after 3am on the 1st, a time advancing to a little before 2am by the 31st. An hour before sunrise Jupiter will be easily visible quite high in the sky to the northeast.

The planet starts May in Aquarius but moves into Pisces on May 3.

In Pisces Jupiter will close in on Uranus with the two 1 degree apart on the last morning of the month. At magnitude 5.9 Uranus will be an easy binocular target. An hour or so before dawn Uranus will be to the lower right of Jupiter. There will be no stars of comparable magnitude between the two planets, so identifying Uranus should be easy.

Earlier in May the 18% lit, waning moon will be some 7.5 degrees from Jupiter shortly before sunrise on the morning of the 10th. The two are a little closer earlier in the morning.

MERCURY was at inferior conjunction on April 29 so will become a morning object in May. Early in May it will rise only just before the Sun and not be visible. During the first part of May, it will rapidly move away from the Sun, rising two hours before it by the middle of the month. As a result, Mercury will be easily visible 45 minutes before sunrise, low, in a direction between east and northeast. It will remain observable for the rest of the month.

Mercury will brighten from magnitude 1.5 to 0.3 during the second half of May. It will be the brightest object low to the northeast. It will move from Cetus to Aries on May 23. Mercury's easterly movement through the stars will take it between Hamal in Aries and Menkar (Alpha Ceti) in Cetus. Hamal, magnitude 2.0 will be about 14 degrees to the left of Mercury, Menkar, magnitude 2.5, about 10 degrees to its right. The two 15

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stars and the planet will be almost in line on May

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OUTER PLANETS URANUS is in Pisces and visible in the morning sky. As noted above, Jupiter gets to be within a degree of the more distant planet by the end of May, making it easy to locate in binoculars.

NEPTUNE, also in the morning sky, will be about 30 degrees to the left of, and a little higher than, Jupiter. Neptune is in Aquarius close to its border with Capricornus.

BRIGHTER ASTEROIDS: (1) Ceres is a late evening and morning object in Sagittarius. It brightens from magnitude 8.2 at the beginning of May to 7.6 at the end.

By then it will be slightly brighter than Vesta.

Ceres remains fairly close to the 2.8 magnitude star lambda Sgr (Kaus Borealis). The two are just over 3 degrees apart on May 1, increasing to 5.5 degrees on May 30.

By the end of May Ceres rises soon after 6 pm so will be observable by mid evening.

(2) Pallas is in Serpens at the beginning of May but moves into Corona Borealis on May 10. It will then be some 2 degrees from the brightest star alpha CrB magnitude 2.2. Pallas will only cross a corner of the constellation before it moves on into Boรถtes on May 27. These are northerly constellations, as a result Pallas will only be above the horizon for a few hours as seen from NZ and keep low, especially as seen from the south.

The asteroid will rise shortly after Ceres, but set in the morning well before sunrise. Its magnitude will drop from 8.7 to 9.0 during May. (4) Vesta is in Leo and will fade from magnitude 7.4 to 7.7 during the month. It is an evening object, fairly close to Mars. By the end of May the two will be 7.5 degrees apart with Mars to the left of Vesta mid evening. Vesta will of course set at a similar time to Mars.

More details and charts for these minor planets can be found on the RASNZ web site. Follow the link to asteroids 2010 COMET C/2009 R1 (McNaught) is expected to be the brightest comet in the late May sky when it is expected to be at magnitude 8.4. However it will be very low in NZ skies. It then rises about 5 am at Wellington, and will be low, between to the north of northeast an hour or so before sunrise.

COMET 10P/Tempel is predicted to brighten from 10th to 9th magnitude during May. For most of the month it will be in Aquarius, although it crosses a corner of Capricornus in the second part of the month. Late in May the comet will be 4 degrees below Neptune and some 30 degrees to the left of Jupiter as seen an hour or so before sunrise.

More details and charts are on the RASNZ web site. Follow the link to Comets 2010. http://www.rasnz.org.nz/ 16

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A review so far!

We have had four public observing sessions scheduled during April plus a telescope workshop.

The first session 10th April included the workshop, one member counted 15 telescopes during the workshop, a great turnout, several members were on hand to help the public with there telescope.

Help included setting up and aligning finderscopes, setting up equatorial mounts, explaining about which eyepieces to use.

For the celestron fans we even had a Orange Tube C8 there, several members assisted the owners to get the scope up and running.

It was pleasing to see so many members of the public turn up, we hope to see many of them join the group.

At about 7PM observing got under way, seeing conditions were excellent, main targets were mars, Saturn and its moons, and the Orion Nebula. A very good evening viewing.

The session on the 17th April was clouded out, but about twenty members of the public turned up at 8PM, several members were on hand luckily to talk to them, in fact the discussions went on for about an hour; again its likely we will see many of them along at our next monthly meeting on the 30th April.

Thanks to those members who give there time to help.

More photos can be seen here: http://www.flickr.com/photos/scastronz/ We have two more sessions to go this month for Global Astronomy Month. 

Friday 23 April, from 7pm – Public Star Party at Geraldine township. South Canterbury Astronomy Group will be available with telescopes to let the public view the night sky. Location corner of Hislop St and Cox St Geraldine.

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Saturday 24 April, from 7pm – Public Star Party at South St Reserve. Open to everybody, your chance to look at the night sky through a range of telescopes. This is a real dark site, you will see a lot of detail! South Street reserve is located behind the Caledonian grounds Timaru.

Click here for maps for these two events.

GAM flyers sponsored by www.nztelescopes.co.nz

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S.C.A.G website - www.scastro.co.cc

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Our Sun

Image sourced from http://sohowww.nascom.nasa.gov/pickoftheweek/ The largest eruptive prominence observed in years blasted into space (April 13, 2010) and SOHO was lucky enough to have caught a key moment of it. As observed in extreme UV light, the plasma cloud was caught about mid-step in its liftoff above the Sun's surface. (Ground-based observers says the eruption took about two hours.) It was not obvious what triggered the breakaway, but it may have been associated with a coronal mass ejection (CME).

Regards

South Canterbury Astronomers Group www.scastro.co.cc The Secretary 28 Kiwi Drive Timaru Ph 03-6883735 Email: langwood@xtra.co.nz 18

S.C.A.G website - www.scastro.co.cc