Imaged the Seagull Nebula (IC 2177) in narrowband over the course of six nights in February/March 2021. The image were captured using an APO refractor and full spectrum modified DSLR through two dual narrowband (Ha/OIII and SII/OIII) filters. This is a tough target from my backyard imaging location, with only ~2 hrs of visibility per night. This was my second attempt collecting SII images for use in generating SHO pallete images. This is the SHO palette image. Individual narrowband images posted under:
https://astrob.in/joi9l0/0/Imaged with WO GT81 at F4.7 (382 mm focal length) using Flat6A II field flattener/0.8x reducer, Optolong L-Enhance dual narrowband filter (for Ha and OIII) and IDAS NB3 dual narrowband filter (for SII & OIII), and full spectrum modified Nikon D5300. Total integration time of ~11 hours:
Ha/OIII data: 54 subs at ISO400x360 sec
SII/OIII data: 60 subs at ISO400x360 sec
Starting with individually processed Ha, OIII, and SII images generated the SHO image using the following steps in PI:
(1) Used Linearfit to equalize the images (using Ha as the reference)
(2) Used the SHO-AIP script to generate the SHO image (Ha for luminance, R=SII, G=Ha, B=OIII)
(3) Reduced the magenta tone of the starts using a colormask (set to magenta) and several iterations of the morphological transformation process
(4) Tweaked the color palette from green dominated to more orange dominated by first using Curves Transformation in Hue mode followed by SCNR to remove green
(5) Color saturation boost
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