Originally, telescope to camera adapters were of the "T mount" variety, which used an 42x0.75mm threaded mount and inserted into a telescope eyepiece tube.
A number of manufacturers (William Optics for one) now offer telescopes with 48mm threads that you can screw an adapter onto, and use the camera's native mount on the other side in place of an eyepiece.
So if you have a Nikon "F" adapter, you would thread it onto the telescope, and use the Nikon body to attach to the adapter, allowing you to use the telescope itself as a really big honkin' lens.