How much zoom will a telescope give my camera?

My telescope is a 6 inch reflector with a 1200 mm focal point, D 150. My camera is a Nikon D5100. With the right t ring adapter, what kind of magnification am I looking at and what kind of detail will I pick up on the moon? Mars? Jupiter?

Normal for that camera's lens is an 18 to 55mm focal length small zoom.
http://www.nikonusa.com/...d5100.html
So for 1200mm then 1200/18 to 1200/55 would mean 66-2/3rds to 21-82/100ths times more magnification with your telescope than you usually get.

"Zoom" refers to lenses which vary their focal length. The word you should be using is "magnification." A telescope used with a camera can give a variety of magnifications depending on the eyepiece and camera lens used (if any). Most astrophotographers use the camera without lens or eyepiece at the telescope's prime focus, but this often is not possible with Newtonians because their focusers are set up for visual observation, and don't have enough back focus for a camera. This is a very complicated area, and I suggest you do some reading. There are several good chapters on astrophotography in the book below.