[Omaroo (Chris Malikoff)]

Matt - Discount the C8 straight away - IF it is collimation. I have many happy snaps though mine at bright objects and have not encountered your experience. Even if I way-overexpose a super-bright object (Venus, Jupiter, Sirius, etc) I just get an overexposed image in the center where the object lies.

Because your aberration is offset, I'd try running the image again and then have a look at the result straight away on your LCD (or on your laptop screen) to make sure you can replicate the problem.

Could you then try spinning the imaging train (it'll be a tad loose in its visual back threads) 90 degrees in reference to the scope, starting with the focal reducer/SCT interface - keeping the filter and camera in line with the reducer as they originally were, and take another exposure. If the aberration has moved then I guess you know it's probably not the SCT.

Repeat by now spinning the camera and filter around an additional 90 degrees by spinning the train at the reducer/filter interface now. Take another image.

Lastly, to the same with the camera.

It may be a clunky method, and by virtue of the fact that by loosening items along the chain you will be altering your focus it'll be difficult - ut you have to start analysing it somehow!