Is this difficult to set up if you have the right scope (one that moves automatically to adjust for the earth's rotation)? How much does it cost (ballpark) to do it right?
Well, depends on what sort of time exposure you're talking about. If it is a short exposure, say a minute or less, you point a decent SLR with a 50mm lens at the sky and open the lens for a minute and close it. No telescope needed at all (just be sure to set the camera on something steady like a tripod, and don't touch it with your hand). If you use ASA 1000 or faster slide film, you should get nice sweeping shots of the heavens, with lots of stars... assuming it's a clear, dark night.
But if you want to take a photo THRU the telescope of a planet, it gets trickier.... the exposure will usually be pretty short (depending of ASA speed, etc.) The problem with short exposures is that the mirror retraction mechanism of the SLR camera causes vibrations that will ruin the photo, so you have to cover the end of the scope (a black felt hat is standard procedure), open the shutter, pull the hat out of the way AND replace it while hand timing the exposure, then clsing the shutter.
Worse still, if you want to photograph faint "deep space" objects (nebula, galaxies, etc.), it gets REALLY tricky First you have to align the scope/mount with the polar axis...... this is a non-trivial task that takes some practice. Then you have to point the scope in the right part of the sky where the object is. Then you have to select a guide star, put your cross hairs on it, and track it with a hand controller while the camera lens is open.
If you can do that for two hours while the temperature is freezing, and manage to not accidently bump the scope during exposure, or not have an airplane fly thru the field of view with it's landing lights on, and the lens don't fog up as it cools off, and you have the right exposure, etc., etc., I'm sure you'll get a WONDERFUL picture......
Perhaps you can now appreciate why amateur astronomers often take dozens and dozens of exposure to get just one that comes out "right."
The new CCD detectors (used in lieu of cameras and film) make things much easier, but it still is lots of work.
Cost: well, "sky's the limit," as they say. A good simple SLR with a MANUAL (NOT electric) shutter is the starting point.
Check with any decent library, book seller, or Amazon for books on the subject. I would advise reading one before spending any money.
Warning: the above information is based on what I've read on the subject: I'm not an astrophotographer, amateur or otherwise.