Padraic M

@Astrowal I know what you mean - I've seen that with my Celestron 8" SCT and a Canon 400D.  The picture at night is generally fine, but I use flat frames to sort out the vignetting (as well as darks etc.)

There's an adapter that lets you connect a DSLR directly to the rear cell of Celestron SCTs by removing the visual back:. Might be worth a try.

https://www.celestron.com/products/t-adapter-for-schmidt-cassegrain-telescopes

FIrst off, I'd agree with the comments on the HEQ5 mount - best piece of kit I have, but I get a work-out every night carrying the parts downstairs and outside, then back again. The tripod and telescope are both fine for one trip. The mount head is very hefty and is a trip all to itself. Then the counterweights on this are very heavy! One in each hand is a challenge. But, it's a very solid mount and tracks well. I'd recommend it a lot, but just be aware that it's a luggable rather than a portable.

Secondly, make sure you understand Vlaiv's post about FOV above. I didn't, and managed to spend lots of money on a 2000mm SCT and a small-sensor dedicated astro camera. Now I can get hi-res pictures of a flea's ass on Aldebaran, but tough luck if I want to catch anything wider than that. My Canon DSLR is too old to integrate with Astrophotography Toolkit so I need to upgrade that. But, I have some nice Canon lenses, so the cheaper option for me in the short term is to use the astro cam with my 70-200mm F/4 L USM with appropriate adapters and a tripod mounting collar. This is while I save up for a new DSLR, and/or an ED refractor scope. It's a bit bizarre that I will end up using my old Newtonian reflector (with a modified Logitech webcam) as a guidescope for the piggybacked Canon lens!

Of course, you haven't mentioned autoguiding. The HEQ5 tracking is good but not perfect, so depending on the focal length of your scope and your expected exposure time, I would suggest you will need an autoguiding solution.