The nature of astrophotography for most people is that they have bought a scope for visual use and then want it to work for astrophotography. However, in terms of design, there's a gulf of a difference between the minimum requirements for each. That's not to say that you can't you can't take any images without spending money on gear; rather, you have to be selective on what sort of imaging you want to do.
Remember one thing though, astrophotography is only as good as it's weakest link. For most people, that's the mount rather than the optics. Most telescope optics are pretty good now. However, a massive difference exists between mounts and this is something that most of us starting out never fully appreciate.
If you put a top of the range ccd camera & scope on a poor quality mount, you'll only get poor quality images. However, if you get a cheaper ccd camera & optics on a good quality mount, you'll get significantly better images.
  