You may be surprised to know that a key tool in astrophotography is the lowly USB webcam. In fact, most amateur lunar and planetary photography is done with webcams: the Celestron NexImage Solar System Imager, widely considered the best camera of its class, is from what I’ve read, essentially a Philips ToUCam Pro modified to fit into a 1¼-inch eyepiece barrel. Webcam astrophotography is essentially a low-cost exercise in adaptive optics: the camera shoots 640×480 video, and you use software to select the best frames (shot in rare moments of atmospheric stability), stack them to reduce noise, and apply an unsharp mask to draw out features. The results are surprisingly good, considering. (For more on lunar and planetary imaging with webcams, see these presentation slides (PDF).)
The software is the key link, and of course the fact that I use a Mac complicates things somewhat, because the telescope companies bundle their lunar and planetary webcams with Windows-only software. Doing it on a Mac requires a couple of extra steps.
Stop right now and read Webcam Astrophotography on the Mac, which covers the same ground that I’m about to (and is actually written by someone who knows what he’s talking about).
So if I want to use the Celestron NexImage with a MacBook (which I’m kind of on the verge of buying), the first step is to install a webcam driver. Celestron doesn’t provide one, but two sources of third-party USB webcam drivers for the Mac are available: Macam, which is open source, and IOXWebcam X, which costs money. Neither mention any astronomical cameras, but they both support the Philips ToUCam series on which the Celestron NexImage is based. There are reports that IOXWebCam, at least, works, but there’s a catch: version 1.1 is PowerPC-only and works under Rosetta, but won’t work with Intel apps; version 1.2 does but is in beta.
For all my searching I can’t find anything better at the entry level. It’s different for other cameras. iCCD controls Starlight Xpress astronomical CCDs, which are top-level and hella-expensive; they’re for long-exposure deep-sky photography, not stacked images of Mars, Jupiter or Saturn. Astro IIDC controls FireWire cameras, which are a few times more expensive than entry-level USB webcams (but far less expensive than an SBIG or a Starlight Xpress).
But once the images can get on the computer, there’s some software available for stacking and processing them. The popular Registax is Windows-only, but AstroStack is a cross-platform Java app; it’s also commercial software as opposed to the freeware Registax. Another one I’ve heard good things about is Keith’s Image Stacker, which is shareware. These apps would also stack images from other sources, such as, say, 30-second exposures from a Nikon D40 plugged into the back of a telescope. For example.