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Hi Josh,
I have the same configuration, and experienced the same issue. Short exposures resulting in better results, with +60 sec exposures showing significantly worse results in CCDINS.
Peter's suggestion may be right, and we may not have the same fault, but I can tell you what you should check first before losing months trying to fix CCD tilt that may not be the problem.
The CDK has beautifully and accurately made parts, and I've measured everything of my CDK in the quest to remove my problem. In my case the whole scope was not assembled correctly, with a bad optical alignment causing the issue. What to first check...
You should check using a collimated laser, that its beam centers on the secondaries centre marker. You should rotate the laser in it's seat to ensure the result. If your laser is out, see that the drawn circle revolves around the centre marker.
If the alignment is precise, tilt may be the issue, but I'll guess this alignment will be out. Considering the design, it may seem that few adjusts are available, and that's true, but you seriously need that dot centered.
From your images, I'll guess your about 5mm to 10mm out. First, you could try adjusting your spider vane lengths. You should only make small adjustments, as large adjustments will make your vanes tilt, and star defraction spikes will deform.
Not to lose time on this not being the issue, I'll stop here. You can PM me and I'll correspond full details here to reshape the CDK.
I have now a very flat CCDINS result, and collimation below 1.
Good luck,
Steve
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