Quote:
Originally Posted by Martin Pugh
I did have to do some cropping, not because of aberrations but because the flats either under or over corrected. I have to do some more research on taking flats with a DSLR when attached to a scope, it is not as straightforward as I thought it would be.
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The problem could be mechanical vignetting as opposed to optical. I’ve noticed this when connecting my Nikon D810 to faster telescopes where both the F-Mount opening AND the box that the sensor is contained with cause vignetting. At F/5 it is correctable and only causes some 15% vignetting but when you get down to F/2.2 and vignetting gets closer to 60%+ (I’m guessing here) flats become more and more problematic.
Canons do have a wider opening than Nikon’s but if you’re using a M48 connector some 55mm from the sensor that’s going to cause a bucket load of vignetting at F/2.2