G'Day Paul.
My recommendations would be to use a web cam to capture at about 25 to 30m focal length. With your scope a 5x powermate would be a good start for high res work, but I would suggest you make your first few mosaics at the native focal length of your scope. That way there are fewer final images to stitch, and you will encounter some problems so its a less frustrating way to learn those lessons. (I am thinking of things like parallel sweeps of images that for some reason aren't parallel so you end up with holes in your data, etc
)
Autostitch is an excellent tool for stitching mosaics, there is a free trial version but it only handles JPEGs.
Photoshop CS3 is much improved over CS2 for stitching images. I have been testing it out and haven't been able to fault it yet.
Enjoy,
Al.