Important Announcements

	S*T*A*R NEEDS YOU! to help out the kids at the Forrestdale School in Rumson.These kids are great, very much interested in whatever astronomical topic we have to talk about. You don't have to be an expert in anything to do this, just have some interest and enthusiasm. Tell them about what you do, how, and why. They'll ask you enough questions to fill the time. We need someone to teach for 1 hour on one Saturday morning in March. Contact Dan Pontone for details.
	Our next meeting will be on Thursday, March 2nd, at 8:00 PM at the Colts Neck Fire Company #2 on Conover Rd. in Colts Neck. Our speaker will be Dr. David Segelstein, who will give his highly acclaimed and interesting talk on astrophotographhy. The few S*T*A*R members who got to preview this say it's a presentation not to be missed. If you didn't make the last 2 meetings, note the change in day of week, time, and location! Directions are available on our web site or hotline (see the end of this newsletter for contact information).
	We need articles for the Spectrogram! Would you like to write one? See http://www.starastronomy.org/Library/Spectrogram/author.html for article submission guidelines, or ask Mike Lindner about it at the next meeting.

News & Events

	March 11th Messier Marathon at Coyle field. See article below for more information.
	March 15th Star party for Holy Cross School in Rumson. 7-9 PM. Scopes needed. Contact Dan Pontone for more information.
	Andy Zangle is collecting members' cell phone numbers as part of making up an ``observers' list'' for people to call when they are going out observing. If you are interested, please contact Andy.

Notes from February

By Dave Hayden

• Astra hosted a planetarium show on February 11, free to S*T*A*R members.

• Larry Campbell hosted a Star Party for the Holmdel Indian Hill School 3^rd grade on 2/8.

• Dennis Larzik is getting a 6 ft. dome in March and is looking for help installing it. He plans to put a 10" LX-200 inside the dome.

• Mike Lindner got the solar filter material for those who ordered it. He showed us his filter. Mike warns that you should block or remove your finder when observing the sun, and check your filter EVERY time you use it for pin holes and other defects..

• David Britz suggested creating a filter for your finder and surrounding the filter with a large obstruction to find the sun. Mike says you can also just move the scope until it's shadow is smallest.

• Steve Walters spoke about the Messier Marathon. This is an annual event where you try to see all Messier objects in a single night. See the article below for more information.

The best times to try the marathon this year are the nights of 3/11 and 4/1. This year, you can also see all the planets. Steve advises planning to attempt the marathon. Get one of the books devoted to the subject. Steve will be going to Coyle field this year.

• Steve has also convinced Dorbrook Park to let us use the park another 4 nights a month. This brings our allocation up to 8 nights a month. Thanks Steve!

• Several people passed around photos from the Lunar Eclipse.

• Joe Cascella spoke about the South Jersey Star Party. It was wet this year, but folks had a good time camping in spite of it all.

• Glenn Fisher showed his video from Jersey StarQuest.

The speaker was Joe Cascella, who spoke about lunar eclipses. Lunar eclipses occur when the moon passes through the earth's shadow. They can be seen from anywhere on the night side of the earth. The color during totality comes from sunlight refracted through the earth's atmosphere. Eclipses don't happen every month because the moon's orbit is tilted about five degrees from the ecliptic, so it usually passes slightly above or below the earth's shadow. Even so, there are three to seven partial lunar eclipses each year.

Why a Marathon?

By Michael Lindner

From 1758 to 1782, a French astronomer named Charles Messier made a list of objects that could be mistaken for comets through his telescope. Messier wanted to become famous for discovering comets, and he didn't want to waste his time looking at these objects by mistake..

Even though he never became famous for his comets, Messier's list became well known as a collection of some of the most beautiful nebulae, star clusters, and galaxies in the heavens.

In the 1960's it was noticed that each year in March and April an observer can see all (or nearly all, depending on location) the Messier objects in a single night. The Messier Marathon was born! Quite simply, it is a friendly star party where the object is to see as many of the Messier objects as you can find in one night.

Why participate in a Messier marathon? It is an easy observing program, so that even a first time beginner can do well. It is also tough enough to find all of them so that even experienced observers will be challenged.

Of course, even if you only see 20 or 50 of the objects that night, you will have seen 20 or 50 more than you would if you stayed home (I found 56 at my first marathon). It's a good way to hone your observing skills, learn your way around the sky and learn to distinguish different kinds of objects. Finally, it's a way to get back to the roots of astronomy; a bunch of friendly people under a beautiful night sky, enjoying what nature has provided.

This year the best weekend dates for holding the marathon are March 11 and April 1, and S*T*A*R plans to be out both nights if the weather cooperates. This is also a good year to have an all-planet marathon, since all 9 planets will be visible on these nights as well.

For more information, contact Steve Walters or any S*T*A*R officer. All you need to particpate is a telescope (any telescope will do) and a book or chart of Messier objects. My favorite reference is Harvard Pennington's ``The Year-round Messier Marathon'', published by Willman-Bell http://www.willbell.com/ or (800) 825-STAR. It's a good book for observing Messier objects, and if you order it soon, you should be able to get it by the night of the marathon.

I Want to Do Astrophotography - What do I Need?

By David Segelstein

One of the most frequently expressed interests in amateur astronomy is the desire to take photographs through or with a telescope. Consequently, a large number of questions from beginners (and others) ask what equipment is needed for astrophotography. Almost everyone underestimates what equipment is needed, how difficult it is, and especially how much they need to spend for this capability. The typical question is ``What telescope should I get to be able to do astrophotography?'' The answer is it almost doesn't matter what kind of telescope you start with. Except in special cases, the single most important piece of equipment is the mount, and most mounts that are adequate for astrophotography are more expensive than most telescopes.

What do you want to photograph, and how?

There are a couple of questions you need to answer before you decide what equipment you need:

1. What do you want to photograph - star trails? constellations? the Milky Way? the moon? diffuse nebulae? planetary nebulae? planets? galaxies? (These are in increasing order of difficulty).

2. What medium are you interested in - film? CCD? video?

What objects?

Let's take the first issue - what objects do you want to photograph? There is a wide range of object sizes, and this will affect how you can photograph them. Galaxies, planetary nebulae, and some diffuse nebulae are all fairly small objects (in angular dimension) - usually less than a degree or so. (Planets are even smaller, and are discussed below). These require some magnification in order to yield a large enough image scale to be reproducible in print, slide, web image, or other format. This means you will be imaging faint objects through the telescope as a prime focus instrument. Photography through the telescope is the most difficult kind of astrophotography. It requires the most precise tracking and stable mounting.

The moon is a special case because it is about the same angular size as these other objects (about 1/2 degree across) but is very bright. That means it does not require a long exposure, and precise tracking is not required (except for lunar eclipse photographs, in which the moon is very dim). Planets are another special case, being very bright but very small (less than 1 arc-minute in diameter). They also are most affected by "seeing" (turbulence in the earth's atmosphere). They require short exposures, high magnification, and most likely the aggregation of multiple images to produce an acceptable result. This means you will be using the telescope objective and an eyepiece to project and magnify the image. If you intend to use a CCD camera, which may have a very small but high resolution detector, planetary images may be feasible without eyepiece projection. This area of astrophotography is very specialized, and even those using CCD cameras will typically not use the same CCD cameras that others might use for "deep sky" objects (galaxies, nebulae, and star clusters).

Large, diffuse nebulae, constellations, and the Milky Way are good candidates for a separate camera and lens. The focal length lens you want to use will depend on the size of the field you want to capture. A typical 35mm camera and 90-100 mm lens will provide approximately a 30 degree field of view. Constellations are sometimes larger, so you would need a shorter focal-length, such as a 50mm or 35mm (or even wider) lens. For some nebulae and star clusters that are only a little more than a degree in angular size it will be necessary to use a camera lens that is much longer, approaching the size of what we might rather call a telescope. In any case, these objects may be captured through a camera lens, and the camera and lens will be riding "piggy-back" on a telescope and mount for tracking the objects. Thus, the mount and drive are important, but require less precision than for prime focus photography. As a special case of piggy-back photography, one can use a camera on a "barn-door" platform - one that tracks well enough to handle short focus lenses. This will not be discussed here, but is a good place to start for photography that involves some tracking.

Star trails are the simplest astrophotographs to obtain. They require only a stationary mount, such as a tripod. A dark sky will help, but is not absolutely necessary. Just open the shutter and wait a while.

How much precision do you need?

It is usually very clear after just a moment's thought why the telescope needs to have a drive for most photography. If the exposure is long enough (and the length of time depends on the magnification), the telescope must follow the object as it appears to move across the sky (as the earth turns). It is often less clear why the scope must be "guided" in addition to simply being automatically driven. The fact is that any "clock drive" will have error. There will be errors in the surfaces of the gears, in the rigidity of the mount (flexure), and in the bearings. This error will cause the objects to move (only slightly if the drive is very high quality, but always some amount) in the field of view. Another source of error, which is correctable to some extent, is misaligning the mount with the pole. This can cause field rotation even in a photograph that is precisely guided. Polar alignment is the subject of another article.

Typical, high-quality, "astrophotography-capable" mounts and drives provide tracking in the accuracy range of 5 to 20 arc seconds. That means that, without "guiding," the drive by itself will keep the telescope pointed within 5 to 20 arc seconds of a given target. With a drive like that, and adequate guiding, you can do the most demanding of astrophotographs - long exposure, prime-focus photography. A good quality auto-guider (such as the SBIG ST-4 or the new SBIG ST-V) can yield better than 1 arc second guiding with a drive of that quality, and that is usually better than the "error" produced by atmospheric turbulence ("seeing" effects) on a star image. If the field of view of an image is 1 degree, and it is recorded on 35mm film, this error will be as small as, or smaller than, a film grain. The result is that any error will not be detectable. Good situation!

For "piggy-back" photography, if you are using a 50mm lens on a 35mm camera for example, the field of view is approximately 50-60 degrees. To get the same kind of undetectable error on the film (less than the size of a film grain), you need about an arc minute accuracy. Some mounts will give that accuracy without guiding. Many mounts that are optimistically called "photographic quality" by their manufacturers give between 1/2 and 3 arc minutes (note - not arc seconds) tracking accuracy. To be sure of good quality piggy-back images with those mounts, you'll need to guide. But the guiding requirements will be less stringent than for prime-focus work.

You want names? I don't get advertising dollars, and I don't work for any of these companies, so I will give you the brand names of mounts that in my experience fit into these categories. If you want 5-20 arc second drive accuracy (of course, this also depends on the load on the mount), you want to look at AstroPhysics (900, 1200), Mountain Instruments (MI-250 or MI-500), or Losmandy (G-11 or larger), or any well-made mount that uses Byers gears. Common drives and mounts that are offered by Meade and Celestron will provide 1/2 to 3 arc minute accuracy. Other things being equal, the heavier the mount, the more likely to provide stability, and the larger the drive gear, the more capable of precise tracking. An alternative is to make your own mount. There are examples of home-made, or custom-made mounts, that are quite good. Whatever you do, you'll want the kind of drive accuracy I've described.

Lunar and planetary photography will require smooth drives, but they need not be as precise, because exposures are much shorter than for deep-sky objects. Stability is important, because the motion of the camera shutter should not disturb the image during the short exposure. This is not a problem for CCD cameras without mechanical shutters (although stability never hurt a photograph). Frankly, I don't know the quantitative accuracy requirements for lunar and planetary photography since I've never done it, but I'm sure it's harder than most people think it is. Note that there are far fewer photographers producing good planetary images than those producing good deep-sky images.

Film or CCD?

Do you want to use a 35mm (or medium format) camera? Or do you want to use an electronic, digital camera that is based on a Charge Coupled Device, or CCD (an array of detectors which essentially convert photons to electrons, and can then count them)? Each has advantages, but the primary advantages are:

• Film can inexpensively record a large field of view with a single exposure (the size of 35mm film is 24mm by 36mm, medium format film is 6cm by 6, 7 or 9cm). The cost of a comparable CCD would be astronomical (as in Hubble range).

• CCDs are linear detectors (they don't suffer from "reciprocity failure" as film does), and are typically more sensitive than film. They also have the capability to provide better resolution than film, since pixels can be smaller than most film grain sizes.

If you can find a CCD chip the size of a 35mm film frame, and you can afford it, by all means get it. It is likely to have better resolution than the film, and you don't need chemistry to process it. On the other hand, you'd be talking about a 10 mega-pixel camera (or thereabouts), which will yield pretty large files for your images. And you'll have to do 3 images (or more) to produce a color image (except for one-shot color cameras). And you'll need filters, and a computer (or two), and ... Oh, and there's the cost factor. The largest commercial chip in common use today by amateurs is the SBIG ST-8, which is 9.2mm by 13.8mm and costs around $8,000 (without filters, computer, etc.). It would take a mosaic of several images by such a chip to provide the equivalent field of a single 35mm frame. And if a CCD chip that size becomes readily available and cheap, the film photographer could go to medium format (up to 6cm by 9cm), leaving the field of view of the CCD in the dust again (assuming the optics of the telescope provide that large a field without aberrations - not an insignificant requirement).

However, the story is not quite that simple. As mentioned, many objects people want to photograph are very small. A "typical" galaxy can be, say, 5 by 15 arc minutes in size. The ST-8 chip on a 1500 mm focal length telescope (60" focal length, like a 10" f/6), will cover about half a degree diagonally across the chip. That's plenty of space for imaging a 1/10th degree by 1/4th degree galaxy. And you'll be able to do it in a few minutes, instead of an hour. Then you can obtain lots of images through various color filters (to be aggregated later in software), and produce a color image in about the same or less time it takes to image the object on color film.

Because CCDs are linear, they yield greater image density for longer exposures, But also, they yield some density for very short exposures. Film has non-linear properties at the short and long end of the time dimension. So a short exposure (say, less than a minute or so) will record less than 1/10th the density that a 10-times longer exposure will. At the other end of the scale, a very long exposure (say, 100 minutes) will record less than 10 times the density of a shorter (10-minute) exposure. You can take lots of short exposures with a CCD, and aggregate them later into a composite image using digital image processing. That, consequently, requires less precision in the telescope drive. Therefore, the mount need not be as substantial as for film photography.

Whether you choose film or CCD photography, you will get good results with proper equipment and with an adequate amount of time to learn your system. This point cannot be overstated. You can find countless examples of astrophotographers who have the best equipment, but cannot produce good results because they do not have the patience and experience with their equipment that is necessary for consistently obtaining what the equipment can provide. (This, by the way, is true for most of us, only differing in degree).

Refractors, Newtonians, SCTs, etc., etc.

What type of telescope should you get (back to the first question)? Great images have been obtained with refractors, Newtonian reflectors, Schmidt-Cassegrains, Maksutovs, Ritchie-Cretiens, Dall-Kirkhams, hyperbolic astrographs, etc., etc., etc. This question only becomes important when you've decided what objects you want to photograph. Remember that focal length determines image scale, and focal ratio determines image brightness (and exposure times).

Looking to photograph the Rosette Nebula (about 2.5 degrees across)? Want to do it on 35mm film? You'll need a telescope with around a 30" focal length. A 4" f/7 refractor, a 6" f/5 Newtonian, an 8" f/3.3 astrograph - these would all be suitable, but would require different exposure times. You can't get that object in an 8" f/10 SCT with either film or a typical sized CCD. Or you could use a 10" f/6 telescope with a camera and 400mm lens riding piggy-back. You'll need a good drive (you need long exposures for film, and even for CCD cameras for this object) and a good stable mount.

Want to photograph galaxies? Don't bother with a 6" f/4 Newtonian, or a 5" f/6 megabucks refractor. That 8" f/10 would be OK, except that f/10 is slow for film. But if you use a CCD camera, it would work. You'll need a really good mount and drive.

Want to take panoramas of the Milky Way? Put a camera and wide lens on top of any decent scope and mount, and guide the image.

Get the idea? Pick the objects you're interested in, pick the medium (film or CCD), pick your scope and mount. Then spend a lot of time.

Alternative Advice for Beginners

What is the cheapest, easiest set-up that would enable you to do astrophotography of several different kinds of object? A small, high quality refractor or reflector of relatively short focal length, and a Losmandy G-11 mount. Cost? Around $2000 for the mount and drives, and whatever you can afford for the scope, as long as it weighs less than 50 lbs or so together with camera and other equipment. Want something better? A Mountain Instruments MI-250 (around $4000) and a larger or better scope, but less than 80 lbs or so. Want more? An Astrophysics 1200 (around $7000) and any scope you can afford up to about 120 lbs weight. Know a good machinist and want to design your own mount? Unlimited possibilities (and cost). All this is exclusive of the extra equipment like camera (film body or CCD), autoguider, guide scope or off-axis guider, etc.

The vast majority of beginners who express an interest in astrophotography will change their minds within a short time. This is not really because it is a difficult and expensive aspect of astronomy. It is mostly because, beginners don't yet know what they like, and what they really want.

If you are feeling the need to get a telescope, unless you have unlimited funds, it is best not to try to start out getting everything needed to do photography. Get a telescope you will use visually, with good optics, and that is portable enough to take to dark sites. Learn the sky, and learn what objects look like and what gets you excited about the activity. You will naturally evolve toward doing the kind of photography you want to do after some informed experience in the activity. Then, start thinking about what it would take to photograph the objects you like, and with the medium you find most interesting. In the meantime, start saving your money. You'll need it.

Constellations for March

By Penny Fischer

This month we will look at the Twins, and an elusive Unicorn.

The Twins, Castor and Pollux, were Greek heros of mythology. They were two of the men that Jason led on his ship the Argo in search of the Golden Fleece. Because Castor and Pollux were able to control the wind and the sea, they were very helpful to the crew, the Argonauts, during rough seas and bad weather.

Castor was a famous horseman while his brother Pollux became a skilled boxer. They were born from two eggs laid by Leda, the Swan, and their father was Zeus. Zeus had seduced Leda in the guise of a swan.

Castor was killed in an altercation with their cousins, Idas and Lynceus. Pollux was so devastated by the loss of his twin brother that he begged his father Zeus to kill him also, so that they were not separated in death.

Although Zeus was a God, even he could not do that. What he could do was to immortalize both brothers by placing them as stars in the sky.

Although Gemini is considered twin children in Greek mythology, in Egyptian mythology they are considered two goats, and in Arabian mythology they are twin peacocks.

Gemini is home to several deep sky jewels. M35 is an open cluster with about 200 stars. It is readily seen with binoculars and is well detached from the starry background, with a collective magnitude of 5.1. The famous Eskimo nebula, Planetary Nebula NGC 2392, lies in this constellation. Magnitude 1.6 Castor is a double star (Alpha Gem)that splits into two blue-white components of 2nd and 3rd mag. Gemini is also the radiant to the Geminids meteor shower, a famous shower in December.

In the southern evening sky is the constellation Monoceros, the Unicorn. It lies between the two dogs, Canis Major and Minor. The Unicorn was first referenced in a star map in 1624, made by Bartsch, who was Kepler's son-in-law. It is believed that the constellation may go back further, although no myths surround this grouping of stars. Historically, unicorn-like animals were found as far back as about 1000 BC from Assyrian paintings.

Monoceros is home to a beautiful open cluster, M50. The cluster has a combined magnitude of 6.3 with most stars being about 9th magnitude. 7' south of the center is a prominent red giant star which contrasts starkly with its blue-white neighbors.

Also in this constellation is NGC 2244 and NGC 2237, the Rosette Nebula. This nebula is more than a full degree across in the sky; five times the size of the full moon! NGC 2244 is the grouping of young stars clustered in the center of the nebula. The stars were formed by the nebular dust and gas, and their light illuminates the nebula. The cluster has a magnitude of 4.8 and is visible in binoculars.

Also in Monoceros. The Christmas Tree Cluster, NGC 2264, is a small cluster of 40-150 young stars, and has an associated nebula with it called the Cone Nebula. The cluster's magnitude is about 5 and the stars are in the approximate shape of a Christmas tree. The Cone Nebula is a dark nebula.