Does anyone know how to get M31 to come into focus on a Canon Rebel T2i using a Sigma 70mm-300mm APO? It's piggyback on my Meade LX200GPS 10" F10 and wedge. So I'm assuming, I need to get the computer to recognize where the stars are, which it won't yet, it hasn't since ever I've tried using a wedge. Then if the pointing accuracy is good goto a bright star, use a mask for focusing if needed and then go back to M31? PS: I'm also using the Canon Utility program that sort of gives the T2i controls that some CCD's have... like it shows a histogram, allows you to control time and exposure and use liveview. Unfortunatly liveview won't always show very dim items even though focused well.
I would use any bright star to lock your focus first (with mask if you have it) then move to M31.
Have you tried Astrophotography Tool software?- it supports most Canons and gives you a good screen to help focus with live view and I also use it when I am aligning as it has cross hairs.
You can also control your image acquisition and ISO etc.