I think the first thing to decide is what type of astrophotography you want to do. You can do wide-field with just a camera + lens, which will be the cheaper way to go. Going full-bore into prime focus AP (i.e. camera using a telescope as a lens) can cost a lot more (starting at ~$2K) and there's a steep learning curve.
For wide-field AP, there are a few options:
1.
Static tripod: This is the cheapest option obviously. With a wide-angle lens, you can get decently long exposure to get a few DSOs (Deep Sky Objects, e.g. nebulae, the brightest galaxies). For instance, you can run an 18mm lens at about 1-min exposures without noticeable star trailing. The longer the focal length, the shorter the exposure before you hit trailing. So this obviously means that you cannot get close-ups of DSOs. But it's definitely a good way to start out. Some examples:
Milky Way at 18mm, f/3.5, 54-sec
Andromeda Galaxy at 35mm, f/1.4, stack of 10 10-sec exposures
To really do good long-exposure astrophotography, you need to track the motion of the stars. There are several options here.
2.
Barn door tracker: This is a simple DIY tracker you can make at home -- with the basic version, you manually crank it to track, while some of the more advanced ones incorporate a motor.
More at Wikipedia (the references include links to detailed instructions). I've seen pretty impressive results with barn door trackers, but haven't used one myself.
3.
AstroTrac is a tracking mount made specifically for cameras (in other words, it's not for telescopic/visual use). I have seen stunning images (check out the gallery on the website). It is quite portable, which is useful if you have to travel to get to a dark site. The website is a bit confusing though, in terms of which of the components come together and which you have to buy extra, but it is probably the best bang for buck. The downside is that this has no other uses except for AP.
4. Equatorial mount: An equatorial mount is a proper mount used for telescopes, but you can just get the mount (+ tripod obviously) and get an adapter to attach your camera onto the mount. This will give you the best wide-field imaging since these mounts are very accurate. Decent mounts start around $1K-$1.5K, so it is definitely not cheap. The advantage of going this route is that if you ever invest in a telescope for visual observing or prime focus AP, then you already have the mount. Mounts are heavy, so not very easily transportable. Some examples of AP with camera sitting on the mount:
Andromeda (details at bottom of image), taken by camera sitting on mount
Orion complex (details at bottom of image), taken by camera sitting on mount
100% crop of Orion complex
Besides hardware though, software and post-processing will make or break your images, and that's where the biggest learning curve lies. Again, Jerry's site is a great starting point:
http://www.astropix.com/HTML/J_DIGIT/TOC_DIG.HTM. To get the best out of your equipment, you will need to stack multiple exposures, calibrate with darks and flats, and spend time doing very fine-tuned post-processing in something like Photoshop (always edit in 16-bit -- with all the faint data, AP is one place where 16-bit editing really shines - example (
http://i198.photobucket.com/albums/aa243/FuzzCO/Web/Bit-depth-comparison.gif)). Also, here's a quick comparison of an unprocessed stacked image versus the final processed image (nothing has been added - the data is all there in the unprocessed image, but it's too faint to see): Andromeda (
http://i198.photobucket.com/albums/aa243/FuzzCO/Web/Andromeda-processingcomparison.jpg). Stacking is absolutely the most critical part -- to get good images, you must stack.
For stacking, DeepSkyStacker (
http://deepskystacker.free.fr/english/index.html) is free and quite powerful. For controlling camera settings, Canon's EOS Utility is fine. For capturing (e.g. set to shoot 1-min exposures all through the night) you could use EOS Utility too, but something like ImagesPlus Camera Control (not the full IP program, just the Camera Control part) is a better option IMO.
A few other points:
For AP, you will need to control the camera with a computer. Shooting through the night = a lot of files = lot of card space. Controlling through the computer = not disturbing/shaking the camera.
Focusing will be your hardest challenge. Several ways to get it right. Using EOS Utility, use LiveView at largest zoom and point at a very bright star - move the focusing ring until the star is the smallest size. Take a few shots between adjustments and compare to see what works. Since cameras focus beyond infinity, you cannot just turn the focus ring all the way. Also, as temperature changes, the focus point changes, so you might lose focus through the night. Good idea to check focus every now and then (at least through the largest temp drop).
Aperture: Obviously lenses are sharpest at less than wide open. The effect really shows up in AP. If you shoot at the widest aperture, you may find bleeding around the brighter stars and distortions around the edges. Stop it down a bit for better results (how much to stop it down will depend on your preference + how much light you need to gather to capture your target).
Definitely turn off any IS. Also turn off any in-camera noise reduction (which, despite its name, actually adds noise).
There's a ton to fine-tune in AP. I've only been at it for a few years, but even then I've improved in leaps and bounds by reading a ton. Let me know if you have more questions on any of these.
I enjoy all of the astro-photos in the forum. Also, I am glad you asked these questions, because mine are similar. I have a feeling that the initial investment for equipment may be overwhelming. I may be wrong though. 