ASI2600MC Pro blotchy flats

Maru.

Regarding the subject, I bought ASI2600MC pro at the ZWO online store in Feb 2024 and just found flats has problem as attached. Therefore, I hope you could let us know how to fix this matter.

The attached picture is a screenshot of ASIAIR mini and I took that by using ASI2600MC Pro, no Filter (the default UV IR window only), EFW, CAA, FF80APO with a reducer. Of cause, I made a measure for light leakage.

I’ve been wondering why the background of my photos is wavy and lately I investigated it and just found the weird flats.

Also, for your reference, I found a thread in CloudyNights, which was created by a user has the same problem with mine.
He said he inquired that to ZWO, but there is no update.

Thank you very much.

R0k9pZfT

Difficult to tell with the small image, and others here will be more knowledgeable than I. The FF80 is a petzval, isn't it? If so, have you compared without the reducer? Also, depending on the optics, this flat doesn't necessarily look unusual and serves its purpose to eliminate optical oddities. Maybe somebody here will know what is "typical" for that OTA.

I have the 2600MC-duo and a WO Cat91. My flats are very different (of course). I don't have this visual, but more of a color smear. But we can't really compare them. I'd see what removing the reducer does while waiting for an FF80 owner or ZWO to chime in. ZWO has been absent here for weeks, so here's hoping!

Maru.

R0k9pZfT Thank you for your reply!
FF80APO is an apochromat, but I haven’t compare with the flats without the reducer and how pre-processing goes without the flats. I’ll check it before ZWO team comes back!
And, thank you for the information about WO Cat91! It’s very helpful. Actually I’m a beginner, so I don’t have much knowledge of the other telescopes and I just thought all the flats are concentric circles uniformly.