if the lens doesn't come off the camera (most all P&S cameras), then the only thing you can do is 'eyepiece projection' where you use an eyepiece *and* the camera lens. this works best with camera lenses that have a rather small front element, set for a medium to slightly wide zoom and mounted in front of the eyepiece just about as far as your eyeball would be. all the rules for exposure go out the window, so its usually simplest to use trial and error to get the right exposure, and focusing a rig like this can be pretty tricky, especially if the camera has no provision for manual (or fixed infinity) focus. If you can lock the camera in 'infinity' focus, then use the telescope focuser in 'live view' mode to focus.
Depends on the camera really. Some PnS cameras like a Canon G series have a bayonet mount and can easily use adapters and be used at "prime focus" with a telescope with the tele lens all the way back. Ebay has quite a few solutions albeit some are a bit pricey. Still better than eyepiece projection just IMHO.
Edited by leveye, 04 July 2017 - 02:00 PM.