Shahd

I processed the data from last night, and it worked! thanks a lot

The distance is roughly 1.5 cm, which means it's either the L filter or the wheel that moved. Anyway, I tightened and changed the L filter position and will take new images and flats tonight. Hope this resolves the issue Thanks a lot!

Yes, I calibrate them with biases.

I take them using SGPro flat wizard, t-shirt and an iPad.

I forgot to mention that this issue is only seen with the Lum filter, flats correct RGB filters perfectly.

Hi I have this issue where flats correct some of the background but make dust donuts look much worse. The problem is exaggerated by applying the DBE (and ABE) process in Pixinsight. Here's the autostretched, calibrated Lum before and after DBE: and here's the stacked Lum without flats, also before and after DBE: I tried preprocessing the images in both Nebulosity and Pixinsight with the same results. I usually take flats at the end of each imaging session so I don't think it's a focusing issue. I believe that they were properly exposed (1.17s, 21000 ADU). The master flat looks like this (second image is autostretched): What do you think the problem is? * camera is ASI1600MM-Cool.