Cygnus Loop Narrowband HOO (4 panel Mosaic) (photonroundup)

Cygnus Loop Narrowband HOO (4 panel Mosaic)

I was lucky enough to get a string of SIX clear new-moon nights in late July to revisit one of my earliest DSO targets - the Cygnus Loop! The first time I imaged this was in 2020 using a SkyGuider Pro star tracker, stock 70D DSLR, 300mm lens, and L-Enhance filter. At that time, it was one the longest project I'd attempted (5 nights, ~220 subs @ 240 sec). The result was OK (my limited processing skills back then didn't help), but I was not happy with my effort. It was not long after that session that I decided to invest in my current setup, but I had not returned to image this target since my equipment upgrades (and my move from APT to N.I.N.A. for acquisition).

Total exposure time per panel was not equal because I suspected poor seeing a couple nights and tried to supplement with more time, but in the end I used all frames (the two right hand panels have ~5hr/filter/panel while the left hand is ~3.5hr/filter/panel). Mosaic processing was done in Pixinsight (MosaicByCoordinates + PhotometricMosaic scripts). I think the seams and gradients were much better than my last mosaic project using GradientMergeMosaic.

I tried to use Deconvolution on the stitched linear image (both with and without stars) but the many bright filaments kept producing ringing artifacts, so I decided to skip it altogether. Not sure if that is a common issue on this target or not? After playing with a couple different approaches (ChannelCombination before vs after stretching, with and without star-removal, with and without Local HistrogramEqualization) I settled on a "simple" approach. Combined channels in linear state after some background noise reduction and using a 20/80 blend of Ha/Oiii for green, neutralized background and used PhotometricColorCalibration, followed by an unlinked STR stretch. After that, just some star reduction and a few curves modifications... nothing more!

Original
Final
C

	Distinct awarded users	Total awarded images
Image of the day
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	Image of the day	Top pick	Top pick nominations	Total submitted
Deep sky
Solar system
Extremely wide field
Star trails
Northern lights
Noctilucent clouds
Landscape
Artificial satellite

	Image of the day	Top pick	Top pick nominations	Total submitted
Backyard
Traveller
Own remote observatory
Amateur hosting facility
Public amaeteur data
Professional, scientific grade data
Mix of multiple sources
Other
Unknown

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Status	Advanced success
Started	...
PixInsight job	1DOERGINA6ZR7T0GLIJINRDD5PVBDCVK
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	20h50m43s.60
RA (top/left)	20h49m50s.97
RA (top/right)	20h39m57s.24
RA (bottom/right)	20h51m31s.66
RA (bottom/left)	21h01m45s.27

Dec (center)	+30°53′32″.4
Dec (top/left)	+33°30′10″.5
Dec (top/right)	+29°40′45″.6
Dec (bottom/right)	+28°16′34″.6
Dec (bottom/left)	+32°02′51″.10

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