[cconstantine]

I've seen some pretty impressive stuff done with a relatively cheap / simple DSLR setup.

The basics of astrophotography aren't that expensive, but it gets exponentially more expensive to meaningfully "zoom in". Because DSLRs with typical lenses are pretty zoomed out you can get away with much cheaper gear. You might look into getting a "star tracker". It's like a telescope mount for a camera; it'll keep the still relative to the stars but because they don't need to be as accurate they're far cheaper to make. They'll probably work just fine for your 200mm 2.8 lens for a fraction of the cost of a mount.