NGC 7331 and Environs, Deer Lick Galaxy Group and Stephan's Quintet, LRGB, 18-27 Oct 2017 (David Dearden)

NGC 7331 and Environs, Deer Lick Galaxy Group and Stephan's Quintet, LRGB, 18-27 Oct 2017

I had a lot of problems acquiring this image. Intermittent clouds were an issue, as were the neighbor’s trees. The biggest problem was the flat calibration just didn’t work well. This produced color and brightness gradients I had to try to get rid of in post-processing. I guess I need to take some better flats. (And the overarching problem, a deadline I’m trying to meet for a National Science Foundation proposal on top of a bunch of other things at work!) Overall, it’s still the best image I have so far of this part of the sky. I can see I need to go a lot deeper if I want to do better. Also, maybe using a gain of 198 was not good here. Lower gain with longer exposures probably would have been better. I was really battling the sky glow, especially in the luminance. I’m not exactly in a dark sky site (Bortle orange, probably)!

Date: 18-27 Oct 2017

Subject: NGC 7331 and environs, Deer Lick Galaxy Group and Stephan’s Quintet

Scope: AT8IN + High Point Scientific coma corrector

Filters: ZWO 31 mm diameter unmounted L, R, G, B

Mount: EQ-6 (EQMOD 2.000j)+PEC

Guiding: Orion Thin Off-axis Guider + DSI +PHD 2.6.4.4 (Win 10 ASCOM) using predictive PEC algorithm

Camera: ASI1600MM-Cool, -20 °C, Gain 198 Offset 50

Acquisition: Sequence Generator Pro 3.0.0.2

Exposure: 105x150 L 24x150 R, 27x150 G, 24x150 B,

Stacking: Neb 4.1.6, flats & darks, trans+rot align, Nebulosity 1.5σ stack and align.

Processing: StarTools 1.4.328: Aggressively stretched and deconvoluted L in StarTools. Combined RGB in Neb 4 and stretched, color balanced, deconvoluted (less aggressively) in StarTools. Used Carboni’s Astronomy Tools to remove horizontal and vertical pattern noise in the RGB, and smoothed it out, relying on the L for detail. Several rounds of “Less Crunchy More Fuzzy,” and several rounds of layer-masked curves + levels to get rid of nasty gradients. AstroFrame.

ZWO ASI1600MM/QHY163M

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Status	Basic success
Started	...
Astrometry.net job	1790955
PixInsight job	81I8W0BZAXR73KB2F0D8WLZL4L4YPAQS
PixInsight queue size	n/a
PixInsight stage	n/a

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NGC 7331 and Environs, Deer Lick Galaxy Group and Stephan's Quintet, LRGB, 18-27 Oct 2017

NGC 7331 and Environs, Deer Lick Galaxy Group and Stephan's Quintet, LRGB, 18-27 Oct 2017

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NGC 7331 and Environs, Deer Lick Galaxy Group and Stephan's Quintet, LRGB, 18-27 Oct 2017

NGC 7331 and Environs, Deer Lick Galaxy Group and Stephan's Quintet, LRGB, 18-27 Oct 2017

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