I wanted to upgrade my scope and get something a little better for planetary work. My first large scope. Click on the scope to go to Orion Optic's web site. This scope is a GPX200 Schmidt Newtonian. This means that wide fields of view can imaged and shorter exposure times can be used.
Collimation needs to be very good.
I have managed to get it as close as possible using a sight tube. This can easily be made using a 35mm film canister with a small hole drilled in the top. A very good page by Nils Olof Carlin has all you need to know about collimation, including information on tools which can be made to help. To get better collimation I bought a Cheshire eyepiece. This tool is like a basic sight tube but has a reflective surface and cross hair inside the tube.