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+1 for 100mm APO. Contrary to popular belief, you do need to check their collimation, but once set, they hold it much better than any of the reflectors you mention.
I'd steer well away from a small RC. They require a bit more fiddling to get right and I understand collimation is trickier the smaller the aperture.
Essentially it breaks down like this;
If you want to capture nebulae, you'll get a lot of instant gratification with a 100mm APO. Lots of detail and an image scale that will a) fit larger nebulae in, like n Carinae, M42 and Running man, the entire Rosetta (depending on pixel size, of course) and b) be more tolerant of tracking errors if you don't have the $$ to pay for the mount.
If you want Planetary, the mount becomes even less important because tracking just has to keep the object in frame for a few minutes. But! You'll need longer focal lengths - typically achieved by a combination of powermates and native scope length. You want around 5-6000mm total focal length to get surface detail. A lot of it comes from the seeing. After that it comes from getting lucky breaks in the seeing that last fractions of a second, so you'll want a fast shutter speed. More aperture will give you more light to play with and therefore faster shutter speeds, so a Newtonian may be your best bet here.
But if you really want galaxies (other than Andromeda, M33 and the Magellanic clouds) then I'm afraid there is no help for you. You really need a good mount - there's no getting around it - because you need excellent tracking at long focal lengths. I would spend all your money on a decent mount and just get a non-APO to play with fo the time being. If you have a mono camera with a filterwheel, shooting RGB will ameliorate chromatic aberration somewhat, but to get to those kind of focal lengths with a small aperture instrument will be way *slow. For example, doubling the focal length of a system *quadruples the exposure times. You may get more joy with a newtonian in this situation.
But yes, I'd definitely avoid an RC scope (I have one). They are good scopes and remarkably aberration free, but you'd want to feel very comfortable collimating a newtonian before considering one, and even then the design practically requires a Tak collimating scope to get to star-test stage.
Hope that helps you some :-)
Markus
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