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Generally speaking when starting out in imaging you want a widefield refractor. Why?
Everything is easier - easier autoguiding, focusing, framing, no collimation, no big cooldown issues, not susceptible to seeing, lightweight, portable.
A C9.25 is a long focal length scope. Its heavier, long focal length, suffers from mirror shift, cooldowns, focuser would be inadequate, needs a better mount, etc etc. Everything would be way harder. Especially autoguiding with that mirror shifting around.
So 100-120mm would be plenty. Triplets are usually better than doublets as APO means 3 colours come to the same focus point. Generally refractors are weak at coming to focus in blue hence blue rings around bright stars.
If you need to lower the budget then get a scope 2nd hand from classifieds here or off Astromart.
Put a bit more into the mount and a bit less into the scope. A great scope on a bad mount may be ok for visual but certainly not for imaging.
Others can advise you on the Eq mounts. There seems to be a few of them and I have seen plenty of round star images using them.
The first target is to be able to get round stars at 10 minute exposures. Not so easy.
Use a modded Canon 350D DSLR to start with. It costs very little and gets great results and plenty of support and software. So spend most on the mount, then the scope then a modded DSLR an that will keep you within your $5K limit. Stay away from Newts, SCTs, any mirrored scope as your first scope as you really don't want to get into their complexities as your first setup. You'll have a loss.
There are plenty of widefield images. Its not that widefield imaging is only a beginners task - not at all. Some of the best astro images around are widefield images. They are easier to get started on and get a pleasing result. Forget ideas of close up galaxy images until later on as your interest and gear naturally evolves up to that. There's plenty of interesting widefield targets to keep you going for several years.
Greg.
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