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RGB stars with L-Enhance capture... and PCC...

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#1 sbharrat

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Posted 03 July 2022 - 08:57 AM

Know it is a toss-up between no answers and answers beyond my comprehension on this forum, but hoping for something in the middle fingerscrossed.gif

 

I recently did some L-enhance imaging of Eastern Veil. Part of my workflow uses photometric color calibration and since this was L-enhance, I use the narrowband option with values for R/G/B for the L-enhance. (Actually, I have a separate question on that. Anyone have the exact bandpass widths for the L-enhance?) Anyway, the image ends up looking great but, not surprisingly, the stars are odd colored. Usually it ends there for me with dual band data unless I am motivated enough to capture RGB stars and add it back in.

 

This time though, I did something different. As part of my workflow, I always separate out the stars and process them separately. On a whim, I wondered about running PCC on the stars themselves. PCC is using R-G and B-G color indices to correct the color against the APASS catalog. I wondered if I run PCC on the (odd colored) stars using the broadband setting, wouldn’t it end up correcting the indices to effectively the proper equivalent RGB stars? (Yes, it would mess up the rest of the image, but here I am working on just the stars.) And if the B-G and R-G color indices are set to what they should be, maybe I will end up with RGB stars. 

 

Well the reason I am writing this is that it did produce what appeared to be reasonable looking RGB stars. But I am trying to understand whether this is just wishful thinking or whether it makes any sense. I can understand that since my L-Enhance band passes are very different than the ones used to create the catalog, it is possible that the color indices won't have any kind of linear relationship. But at least for this case, they seemed to. So the color calibration seemed to work. What is flawed about this?

 



#2 BKMaynard

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Posted 03 July 2022 - 09:05 AM

If you're doing scientific spectral analysis on stars it would be a problem, for pretty pictures go for it.


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