Bow Shock Fronts of the Cygnus Loop (Jim Lindelien)

Bow Shock Fronts of the Cygnus Loop

I am in the middle of processing an NB-LRGB of this region and posted this rough starless Ha stack with the thought there might be general interest in the deep field nebulosity near the Veil. It is a view not commonly posted and reveals the gossamer shock fronts at the edges of the SNR's gas bubble into the background material, most likely (I assume) of the Cygnus Nebula cloud.

This imaging run also had the technical goal of comparing 15 minute exposures at gain 200 in 2x2 binning (thus deeper pixel wells) on the ASI6200MM-Pro vs. running 1x1 at 100 at shorter exposure times. I realize the full benefits of CCD binning are lost on CMOS, but the faster download times and much reduced PixInsight CPU time are appealing, and atmospheric seeing did not argue for 1x1 anyhow. I later up-scaled the 2x2 stack with 2x drizzle integration: not with the expectation of more detail, but because it lowers the noise floor by 2 to 3 dB.

For this camera, MaxIm DL and ASCOM ZWO drivers offer a gain range 0 to 100 and I understand the usual logic of restricting the gain range to this. But I like to experiment, and so for this session I switched to the direct ZWO driver under N.I.N.A. to open up the full gain range, then selected gain 200 (0.078 e-/ADU) and chose exposure time to just barely saturate the core pixels of the brightest stars when binned 2x2 (for the eventual starry rendering of this FOV). While modern CMOS sensors have low read noise, long exposures, of course, further mitigate the total read noise accumulated.

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WO Star 71
Narrowband imaging
ASI 6200 MM Pro

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Status	Basic failed
Started	...
Astrometry.net job	3883374
PixInsight job	n/a
PixInsight queue size	n/a
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