50mm f1.8 for Astrophotography I am considering using a 50mm f1.8 maybe even try aN 85mm f1.8 on my Astro FI 102MM Telescope have you any thoughts or suggestions?
I have never taken images via a telescope so this is a whole new learning curve. Need to get my brain back in gear, stopped shooting over 5yrs ago due to the gear being too heavy and my back injury not coping so this will be a much easier way of holding the camera...I HOPE.
I'm not an astrophotographer but I'd like to make sure that you know that there are (at least) two ways to put a camera on a telescope from an optical perspective.

The first is to keep the eyepiece on which produces a virtual image at infinity, and keep the camera lens on, focused at infinity.

The second is to remove both the eyepiece and the camera's lens, which leaves the camera's CCD sensor right on the primary focal plane of the telescope.


The first method is the quickest, and it seems to be called Afocal photography (I didn't know that!). If you are careful and the image is very bright, say for example the moon, then you can just set the camera focus to infinity, hold it up to the eyepiece, moving around sideways until the inevitable vignetting is at least centered, and click! You can try to manage the vignetting by moving the camera closer or farther from the eyepiece. Ideally you want to place the entrance pupil of your camera's lens on top of the exit pupil of your telescope's eyepiece.
I predict you will quickly move to the second method which is called Prime Focus Photography. Find an eyepiece-to-camera body adapter and then you are a bona fide astrophotographer!
If you want to take advantage of your very nice f/1.8 lens then lose the telescope and just photograph the milky way or meteor showers. This works best if your camera can be programmed to take a sequence of regularly spaced images, because you can merge them later with a computer with offsets so that the motion of the stars doesn't produce trails.
For more on all of these, search questions tagged photography here and astrophotography in Photography SE.

For completenes' sake only, I'll mention a third way, called Eyepiece projection. While a properly focused eyepiece produces a virtual image at infinity, if you move it out, away from the telescope, it will produce a real image out past the eyepiece. If you are looking at the Moon or something very bright you could put a piece of paper out a ways away from the eyepiece, say 6 to 20 cm, and with some practice produce an image on the paper. You can then imagine having your camera's sensor at that plane. This gives you more magnification compared to prime focus photography, but it may not be useful magnification!
Further reading:

The Prime-Focus Method
Eyepiece Projection
What is eyepiece projection and how do I do it?
Sky &amp; Telescope's Astrophotography With a Digital Camera
Afocal method
Afocal Deep Sky Astrophotography where you can clearly see what vignetting looks like!