Remember, only a maximum of two students can do a given subject (I might be negotiated on this if it's a comet, which usually changes over time). So, there's a race here - find the cool stuff soon and get your dibs on it!
1. Location Location Location: Your subject needs to be well up in the sky during our 7-10pm (7:30-10:15pm in Spring) class time. 27 degrees "altitude" as we say, as a minimum. During the night, things will be rising in the east, moving parallel to the horizon in the south, and getting lower in the west. Also in the west, we're looking over the lights of Santa Cruz. It's our worst direction. Try to avoid subjects only visible low in the west. Unfortunately, the best stuff in the Spring sky is in the western sky during the last half of the semester, or set altogether.
2. Size Matters! We all know that. Especially here. The sweet spot for size is about 30-50 arcminutes. Below 12 arcminutes is too small if you're shooting with the 8" LXD75 scopes, and below 4 arcmin is too small if you're shooting with the 12" Dome scope. Nebulae which are "too big" are still great - you can always find neat parts to focus on. But star clusters which are too big will look really BORING! You may see in my list (see below) reference to using the 50mm or 100mm lens with our camera. But we will ONLY be using the 12" dome scope and 8" LXD 75 scopes with our CCD cameras. You cannot use the camera lenses except in pristine super dark skies, and even then there's filter problems to worry about.
3. Nebulae are great! They're very colorful (blue for dust, red for hydrogen, sometimes green for oxygen). That means "emission nebulae" (sometimes called "ionization nebulae") and "planetary nebulae" - which are freshly dead stars, and "supernova remnants (SNR's)". For Spring students, nebulae will be concentrated in the early semester early evening sky. If you don't strike soon, you may not have much to choose from.
4. Galaxies are usually small, Be very careful before selecting one; it HAS to be a big one to make a suitable subject. Remember, at least 12 arcmin is the minimum size you can use. Now, if it's a galaxy group or cluster and you can get more than one galaxy in the frame, then it can still make a decent shot. Most galaxies are not very colorful however. Also, check the galaxy type. "Spirals" or "barred spirals" are the best, or "irregular". Ellipticals are BORING! S0's are almost as BORING! Unfortunately, galaxies dominate the Spring semester sky, especially later in the semester. Spring people, try and get your photo's EARLY, when the beauties of the winter Milky Way are haven't yet sunk into the sunset.
5. Comets are Great! They're usuall intense green, and because they change from night to night they are UNIQUE - which is always a plus photographically. If a comet is available, it makes a good project if it's magnitude is less than 9 (meaning it is "brighter than 9th magnitude"). Comet Wirtanen might be worth a try in Spring '08, but Comet Holmes remains the only good choice.
6. Star Clusters are sometimes good. Often not. They're stars, so the colors are subtle. Sometimes they have nebulosity inside them which is a big plus. One even has a planetary nebula (hint - google search that to find which one! It makes a nice Spring photo subject). "Open clusters" are often large and suitable for photography (if not TOO large). Globular clusters are much richer (like 100,000 stars!) but they're all far away and small, and all are yellowish so not very colorful.
Web Sites With Ideas
First, you can find your own websites with google. Use search terms like "best deep sky objects spring" or "best deep sky objects fall" or "brightest nebulae spring" etc. etc. You get the picture. Google is great! The Messier Catalog was made 200 years ago by Frenchman Charles Messier and it roughly the 100 brightest deep sky objects. It's a good place to look for ideas, but they're also pretty done-to-death as far as originality goes. There are many beautiful subjects which are NOT Messier objects, in fact I think many of the best are not Messier objects (they have lower surface brightness and wouldn't show up well in polluted 18th century Paris skies!). The Caldwell Catalog is a good list of the best non-Messier objects and makes an excellent source to search for your subject.
When the website reports the size of the object, you may see arcminutes shown as single quotes, like 35' means 35 arcminutes. Arcseconds will be shown as double quotes. 35" means 35 arcseconds. There's 60 arcseconds in an arcminute so nothing who's size is shown in terms of arcseconds will work for you - it's TOOO small!
Spring Deep Sky Objects from Jerry Lodigruss
The Messier Catalog
The Caldwell Catalog
My personal candidate target list
Another astrophotographer's fav list