When I was thinking of buying a digital camera, I wanted one that would do double-duty as a daytime and a planetary camera. Information posted by scopetronix.com was very helpful. I'll bet they still have a good article on their web site, since they sell adapters that couple such cameras to telescopes and they want happy customers.
Several things to look for: does the camera have threads in front of the lens for filters, or for screwing on additional lens elements? If so, such threads can be used to couple the eyepiece to the camera using the Scopetronix Digi-T system (which I use). Does the camera have a really big lens or a fairly small one? (Oddly, smaller is better here in terms of lens diameter, if I recall correctly.) Does the camera allow manual control of exposure, focus, and zoom? Is most of its zoom optical (good) or digital (bad--digital "zoom" is not really zoom at all--it just takes one pixel and pretends it's two or three or whatever). Does it allow manual choice of image quality? (Digital cameras use data compression to store more frames on a memory card. You want to be able to choose the least possible compression, i.e. highest quality, to save the most detail.) Does it allow manual choice of resolution? Different tasks may require different resolution, ranging from 640 pixels across the long edge of a frame (VGA resolution) to 2048 pixels or more.
Does it have a removable memory card? Almost all do nowadays. Avoid--absolutely avoid--any camera that uses floppy disks for storage. They store 1.44MB. At Sam's club I can now buy a Compact Flash card with 256 MB for my camera. That's a lot of difference in memory. A single frame at highest quality and highest resolution can occupy a megabyte. It probably doesn't much matter what kind of card (such as Compact Flash vs Memory Stick)--three or four different cards are competing for the market, and they'll all do the job fine.
When I bought my Nikon Coolpix 995 about 18 months ago, it was the hottest planetery digital camera on the market, and I paid a lot (about $700). That same camera probably costs half as much now, if it is still made at all, and there are lost of others to choose from. It does, by the way, take excellent daytime photos, too.
First stop: check out scopetronix.com . They've given me good service.