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This is a camera lens Glen, not a telescope, so I can't rotate the camera independently from the lens. Also, none of the optical flaws here were present prior to removing the filters. In discussions with J-P Metsavainio he told me that with his qhy9 when his backfocus distance was out by 1.1mm initially he suffered terrible coma and what appeared to be astigmatism however when he fitted a 1mm thick shim to the setup the lens returned to the perfect performance it was giving with his Qhy8.
I'm still able to focus without problem with this lens, the ngc55 image gave a hfd of 1.2 prior to the imaging run. And my arduino focuser was able to maintain that fairly tightly throughout the run.
My nikkor 85/1.4D however will not focus as it has a hard infinity stop and fails to reach sharp focus indicating the backfocus distance is intact incorrect on account of the filter removal.
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