SH2-119 The Clamshell Nebula in NB (David Payne)

SH2-119 The Clamshell Nebula in NB

Revision title: SH2-119 - Clamshell (minor adjustments)

SH2-119 The Clamshell Nebula (Cygnus) in NB - Aug 2022
Televue 127is - AIS6200MM
A-P 1100 GTO AE, Antlia Pro 3nm NB filters
H,S,O: (3 x 30 x 660ss exposures, Bin 1, Gain 100)
Total Integration Time = 16.5 hours
THe Clamshell Nebula is a large nebula complex (150 x 60 arcmin) in Cygnus, resembling a clam, but maybe an oyster (I see a pearl - 68-Cygni) or a scallop might be better. No matter the bivalve, it lies about 2 degree East of the North Americal Nebula
Conventionally isn't considered a great narrowband target due to a weak OIII signal, but I found the signal significant within the clamshell even though it does reveal any details. I really like this image, despite the less than ideal FOV, because of the sense of movement it suggests - from within the clamshell to the upper right caused by the linear signals in Ha and SII. I also enjoy the "watercolour/ink" effects of the dark nebulosity along the clamshell edge.
The starfield is very rich over the clamshell and it was a challenge to show it, without have it dominate the nebulosity and making it appear too noisy. I originally was intending to use RGB stars, but my RGB integration time was too short, and I was missing a spacer that caused these stars to be too misshapen. Instead I got creative using HOO stars instead. I adjusted the blue star signal with a little GHS stretch, and then used photometric colour calibration (broadband selection) on the NB image to get close to natural star colour. Then I used a multistep process to transfer the stars over to the starless SHO image. The resulting stars are pretty close to natural, even if the nebulosity is in false-colour, Hubble palette.
I am also getting increasingly ok with leaving green in my images.

Original
Final
B

B

Title: SH2-119 - Clamshell (minor adjustments)

Description: Wanted to remove some of the haze that had appeared when stars were added back in.

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Status	Advanced success
Started	...
Astrometry.net job	6154753
PixInsight job	5AIPLI9RG6DHI5B4CAFTOLSU2PLL0I20
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	21h19m03s.543
RA (top/left)	21h25m36s.505
RA (top/right)	21h25m34s.333
RA (bottom/right)	21h12m17s.133
RA (bottom/left)	21h12m44s.286

Dec (center)	+43°54′13″.92
Dec (top/left)	+42°58′06″.10
Dec (top/right)	+44°52′11″.47
Dec (bottom/right)	+44°48′54″.81
Dec (bottom/left)	+42°54′49″.77

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