Stacking issues with rotated field causing luminance lines in Seagull Nebula

Pleiades Astrophoto PixInsight Processing Stacking Artifacts Help Needed
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Benjamin DeHaven avatar
Benjamin DeHaven avatar

Hello! I’m working on the Seagull Nebula, NGC 2335. I took my first batch of images with two dual narrowband filters before deciding I hated the composition and rotated the field for the third and ongoing nights. When I stacked all the data I was left with a very distinct set of lines. I figured it would be just noisier due to less signal but after removing the noise there was very clearly a background luminance difference. Shouldn’t something like local normalization (don’t know, judging by the name) fix this? Is this to be expected or did I have something in Pixinsight WBPP set up wrong… Thoughts? Thanks!

Benjamin

📷 integration2_ADBE_forum_question_about_lines.jpgintegration2_ADBE_forum_question_about_lines.jpgThis is the DBE, blurX, noiseX, starX, and statistical stretched image…

Quinn Groessl avatar
Quinn Groessl avatar

It can only do so much. You have the parts with the original framing getting 1/3 or less of the signal of the parts that were present all 3 nights.

andrea tasselli avatar
andrea tasselli avatar
It depends on the stacking options. I don't use WBPP. You also need to flatten the images before stacking, if they were separate stacks.
Benjamin DeHaven avatar
Benjamin DeHaven avatar

Quinn Groessl · Jan 27, 2026, 01:41 PM

It can only do so much. You have the parts with the original framing getting 1/3 or less of the signal of the parts that were present all 3 nights.

So should I take more of the original framing to equalize the SNR? Think of it as a mosaic at this point?

Benjamin DeHaven avatar
Benjamin DeHaven avatar

andrea tasselli · Jan 27, 2026, 01:41 PM

It depends on the stacking options. I don't use WBPP. You also need to flatten the images before stacking, if they were separate stacks.

Hmmm, I dumped all the .fit files into WBPP and told it to process them all. Do you think I would get a better result stacking each night with a different rotation and then DBE. Then integrate the individual nights together? I have no clue how to stack without WBPP… But this dog can learn new tricks…!

andrea tasselli avatar
andrea tasselli avatar
Benjamin DeHaven:
Hmmm, I dumped all the .fit files into WBPP and told it to process them all. Do you think I would get a better result stacking each night with a different rotation and then DBE. Then integrate the individual nights together? I have no clue how to stack without WBPP… But this dog can learn new tricks…!


Yes, I would (and do) so. Furthermore, I'd replace the black pixels (value) with the average background level value, assuming this isn't zero...
But you always need to flatten the images before stacking.
Mikołaj Wadowski avatar
Mikołaj Wadowski avatar

Local normalization should minimize these artifacts or get rid of them completely.

It’s possible that you’ll be left with slightly sharper gradients around where the edges were but it’s nothing a good background extraction won’t handle.

Well Written Concise
Tony Gondola avatar
Tony Gondola avatar

I didn’t know there was a way to fix this problem. I’ll be curious if any of the above works for you.

Well Written
andrea tasselli avatar
andrea tasselli avatar
Obviously it does.