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Get an Astro-Tech AT8IN..AWESOME scope. with an MPCC it will be perfectly flat.
And trust me, having owned both, the AT is MILES above the Orion 8"!

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When doing DSO imaging focal ratio is critical to keeping the length of subexposures short. Hence the decision, IMHO, is whether the purchaser is all that keen on a long focal length (and implied autoguiding). If yes, then the Newt indeed looks like the way to go. If the OP is simply looking for a means to take great DSO images with the minimum of complexities, then a Canon 200mm/2.8L II looks like a great alternative. I have difficulties seeing where a small APO fits in with DSLRs. f6 is way too slow for pleasant imaging (5 minute subs imply autoguiding using in all likelihood a similar small OTA) and the focal length of around 400 to 500mm is still too short to be much use for lunar/planetary imaging. The 70 to 80mm aperture is also too little for visual use. The Newt would make a better deal vs a small semi APO as regards focal ratio, visual use, lunar/planetary imaging and of course focal length for those chasing seeing-limited DSO imaging. A camera lens would make a better deal for unguided DSO imaging (f2.8 implies one-minute unguided subs) and you get a daytime toy too.

Example unguided images using the Canon 200mm f2.8:


with a 1.4x tele-extender, but still unguided:



In brief, for under $1k go Newt or go camera lens, IMHO.

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