nice mike.. all the modern SLRs are performing at very high levels and the D7000 is well respected camera.
what type of astrophotography are you talking about.. through the lens or through the scope?
you can do some simple stuff with the 18mm end of your zoom but if you want to get serious you'll start spending more than the camera cost on nice lenses. i hope your wife understands that!?
for really widefield/landscape type stuff, the 14-24mm Nikon lens is awesome (see alex cherney's images) but very pricey. cheapest way to start is a 35mm or 50mm for milky way etc. then a nice prime telephoto f2.8 comes next..
Phil