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removing background of Oiii exposures with PI

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#1 SEM4557

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Posted 21 October 2021 - 08:45 PM

Hi folks,

 
I have been trying like crazy to utilize the DynamicBackgroundExtraction tool to extract what appears to be a pretty noisy, stacked Oiii exposure of the Heart Nebula. No matter how many times I use the process, no matter how much I tinker with the settings, I just cannot get rid of the fuzzy background and
subtle gradients.
 
The below is 30 stacked Oiii subs, 300 second exposures at -7 celsius, taken just outside Orlando, FL in Bortle 7 skies. My imaging rig should be detailed below at the bottom of my post. My H alpha exposures turned out real nice and crisp, I was actually happily surprised once I pre-processed those. But Oiii always gives me a real workout in PI, so I'm finally asking for any tips, advice, etc

 

oiii For CS

 

 

Thank you and clear skies!

 

Steve



#2 james7ca

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Posted 21 October 2021 - 10:38 PM

DynamicBackgroundExtration isn't going to remove noise, in fact it usually makes noise more apparent. That said, gradient extraction on a field that is covered in nebulosity isn't that easy and you'll probably be limited to just a few sample points that will only correct smooth, large area gradients.

 

I assume that you used flats, if not that could be part of your issue.

 

Lastly, on many targets the OIII signal is pretty weak and thus it won't appear as noise-free and crisp as the H-alpha. Also, I get the following message when I try to access your image, "You do not have permission to view this image."



#3 Professor2112

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Posted 22 October 2021 - 05:23 AM

Yes, don’t be too worried about the noise, this looks very similar to my Oiii stack of this target.  I’m working on an HOO project, almost identical FOV as your image haha!  When combined, everything went smooth and resulted in a nice image considering the lack of data.  As james7ca said, the Oiii signal is very weak in this target, so it won’t be nearly as nice as the Ha. 



#4 SEM4557

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Posted 22 October 2021 - 08:23 AM

Thank you so much for your replies. Sorry james7ca, for some reason my "AP Issues" album was private (completely defeating the purpose!), but I was able to fix that:

 

oiii For CS

 

 

I did a little experiment where I simply stretched both images before combining them, and it turned out soooooo much better, even with the minimal amount of processing. No noise reduction or anything here:

 

HOO stretched

 

 

Again, thanks a ton for your input. I'd be completely lost without this community!!

 

Best,

 

Steven




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