Quote:
Originally Posted by JA
Hi Mick,
Maybe you are doing nothing wrong. Perhaps look for uncropped Astrobin images using a 0.63x reducer on the C8 with a 1600mm sized sensor to be sure. The images may point you in one direction or another in terms of understanding the root cause of the image edge quality issue.
In any event, using a focal reducer, whilst making for a faster scope will mean you see more of the image circle than you may wish to, revealing all sorts of foibles at the edge of the image circle, even on the relatively modestly sized 4/3 sensor of the 1600mm. I'm not sure another brand of 0.6ish-X focal reducer would help that much, on that sized sensor (~22mm diagonal). Also, perhaps consider trying/researching a 0.8x reducer.
Best
JA
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I’ve scaled the spacing back to 85mm which lands the focal reduction at 0.7. It’s much better to the eye. Will run it through ccdi to make sure tilt isn’t an issue now the oag and visits back has been removed. Will respond once I have quantified the curvature😉