Some of you might be thinking I've gone off the deep end.  But it actually makes quite a lot of sense. A telescope is actually a lens itself.  Now obviously a high quality camera lens is going to perform better than the average telescope.  But what if your camera lens doesn't have enough reach to get a close-up of a subject? The great thing about telescopes is that you can get some great magnification for a very low cost.  A lot of you might have one lying around that was given to you as a gift like I did.  I won't go into details about different types of telescopes.  I will tell you mine is not considered very high end.  It is a small 80mm Schmidt-Cassegrain.  In the photos below you can see it's of the Towa brand. Don't ask me who they are, I got this as a present as a child.  So how did my 800mm Monster do?

Well, the first thing to keep in mind is telescopes are fixed aperture.  The lens is 80mm in this case, and the focal length is 800mm. That comes out to f/10.  Keep in mind in this type of telescope design part of the center mirror is blocked, so I'd say it's practically closer to shooting at f/11-f/12.

What you will need to attach your telescope to the camera is called a t-adapter.  These can be found in your local telescope shop, or possibly even some larger better photography stores.  Mine obviously is for a Canon EOS mount but they are available for other mounts such as Nikon and Minolta as well.  This is the same type of mount you would use if you were to attach your camera for astrophotography as well.

Of course like with any large telephoto lens you mount your camera to the telescope, not the other way around.  I find it much easier to attach the adapter to the telescope first, and than mount it on the camera.