Quote:
Originally Posted by Atmos
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
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Yes, the documentation does talk about it and it is mechanical. The sensor in the 5D is set way back and as you say the M48 wide T-ring aperture is insufficient. I will return to CCD as soon as the right camera is available. But what I was referring to is the method of getting flats. Using CCDAutopilot doesnt work, taking FITS images doesnt seem to work, so presently I am using Canon software but the right exposure length is pure guesswork.
Cheers
Martin