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Concentric Colored Rings After DBE/ABE

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#1 tbrozovich

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Posted 22 February 2020 - 04:52 PM

Hello,

I have been trying to work through an issue for months, after using Dynamic Background Extraction or Automatic Background Extraction, I am left with colored concentric rings. I try to use DBE or ABE again to get the colors out and they don't get removed. I am using bias, dark, and flat frames as well. The flats look good and don't seem to be out of the realm of what I expect to see. 

 

What could be causing this? I have tried shooting in a different location, different city, different bortle zones... nothing is changing the rings.

 

This integration is:

California Nebula shot with a D5100 (unmodded) and Rokinon 135.

195 Images at f2

30 Dark

50 Bias

30 Flat

 

Integration.jpg

 

IntegrationABE.jpg

 

I attached the integration before ABE and integration after ABE. I tried DBE as well with the same results. Any help at this point would be extremely appreciated as I am out of ideas.

 

Thank you,

Tyler

 



#2 sharkmelley

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Posted 22 February 2020 - 06:06 PM

The rings are clearly there in the integration before ABE.

 

The first thing to check is your back-of-camera histograms.  Is the peak of the histogram a good distance from the left hand side for the lights and for the flats?  Underexposed data can lead to concentric rings.

 

Mark



#3 tbrozovich

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Posted 23 February 2020 - 11:14 AM

Mark,

 

Thanks for the reply. I read through a lot of threads that you had responded to regarding this issue. I know my flats are a little underexposed at the moment so I will try retaking flats today. My question is, these threads talk a lot about increasing the ISO for the flats.

 

So should I increase ISO from 200 to say 800 on flats AND lights? Or should I just expose longer and leave it at 200? Or a combination of both. I saw that the Sony sensors had issues and we are not 100% if the Nikon cameras are exactly the same issue but similar. Just trying to fully understand what I need to change on my end. I have a few hours clear tonight I can test out.

Thanks for your help!



#4 sharkmelley

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Posted 23 February 2020 - 11:26 AM

I would keep the exposures the same length and increase ISO for your lights and your flats.   Make sure your flats are properly exposed.

 

Mark



#5 mxpwr

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Posted 23 February 2020 - 11:30 AM

Your could try to set the function degree to 1 in the ABE and see how much of the rings is there in the original data.
Also, if you have some vignetting left, do a division instead of subtraction.

#6 tbrozovich

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Posted 23 February 2020 - 01:31 PM

Mark,

 

I am testing a group of integrations with properly exposed flats using my data from the other night. I will also try a new dataset tonight bumping the iso up a bit. Thanks for the suggestions. 

 

Mxpwr,

 

ABE function 1 still leaves a ton of rings. I am able to get the sky glow out but when stretching further, the rings become destructive to the image.



#7 mxpwr

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Posted 23 February 2020 - 01:51 PM

For testing, it can be helpful to just do image calibration on one image.
Heavily stretch the calibrated image by hand (no need to debayer) and check if it's reasonably flat.
If not, redo flats and try again.


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