With this image my challenge was to deal with a very bright core while still presenting the dimmer, outer gasses and how to blend the SHO data to get representation for all of the colors.
I pre-stretched each channel master leaving the background quite bright and the highlights at .95. Then combined the now non-linear masters using the excellent dynamic NB combination method described here:
https://thecoldestnights.com/2020/06/pixinsight-dynamic-narrowband-combinations-with-pixelmath/This method uses the OIII channel to determine how much Ha, SII, and OIII to blend for Red and Green at a pixel level. The basic formula the author describes worked well for me. That is:
Where f = OIII
Red: f*SII + ~f*Ha
Green: f*(.7*SII+.3*Ha) + ~ f*OIII
Blue: OIII
After that combination was used, I ran a fairly light application of HDRMT to tame the core. This was followed with Starnet++ and PS clean-up to produce a starless.
Noise reduction was applied to the starless image with the PS reduce Noise for the mid-tones and shadows. Highlights received Topaz noise reduction with sharpening turned off and opacity at 85%.
Unsharp masking was use to add sharpening at a 4 pixel span and contrast at a 48 pixel span.
Stars were then added back in and a minimum filter used to reduce them a bit.
Colors were enhanced with the PS vibrance tool, curves in the LAB mode and the final touch of color balance.
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