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Another post of very old unpublished data. The star shapes are not great, but I love the star colors in this field! **
I found some unprocessed data from 2018 in my archives during the write-up of my big Summer mosaic project. Turns out I had 5 hours of OIII data on the Butterfly nebula (IC1318) from 2018 just sitting on my hard drive, why?! Well, the answer became clear pretty quickly: the old ZWO 7nm OIII filter produced large halos around the bright star Sadr, and multiple smaller halos around all the other bright stars in the field.
Re-processing was done in November 2021. I drew a circular mask in GIMP and then used pixelmath to reduce the large halo's brightness. Smaller halos and microlens diffraction on Sadr and other stars were reduced with the clone stamp tool. It’s important to note that these cosmetic manipulations were all done on a starless version of the data. StarNet++ was not yet available back in 2018, and that’s probably why I gave up on this dataset back then.
My false color image uses Ha in red, OIII in blue, and both channels were multiplied to create a synthetic green channel. Starless versions of the Ha and OIII were combined into a luminance layer and white Ha stars are layered on top. Next, I combined this with 30 minutes of RGB data. It’s actually incredible how much nebulosity was captured with just 10 minutes of exposure time per filter!
It’s interesting to see how my processing mindset, skills, and artistic vision continue to change over the years. This image was processed in 2021, below is the 2018 version of the HaRGB data:
Butterfly nebula in Cygnus (IC 1318) 
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