Contains:NGC 7343, NGC 7337, NGC 7335, NGC 7331, NGC 7320, NGC 7319, NGC 7318, Stephan's Quintet, NGC 7317
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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

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

Technical card

Resolution: 4577x3450

Dates: Oct. 18, 2017Oct. 27, 2017

Frames:
ZWO Blue 31 mm: 24x150" (gain: 198.00) -20C bin 1x1
ZWO Green 31 mm: 27x150" (gain: 198.00) -20C bin 1x1
ZWO Luminance 31 mm: 105x150" (gain: 198.00) -20C bin 1x1
ZWO Red 31 mm: 24x150" (gain: 198.00) -20C bin 1x1

Integration: 7.5 hours

Avg. Moon age: 17.64 days

Avg. Moon phase: 23.85%

Astrometry.net job: 1790955

RA center: 339.199 degrees

DEC center: 34.281 degrees

Pixel scale: 0.859 arcsec/pixel

Orientation: 90.455 degrees

Field radius: 0.684 degrees

Locations: Mapleton Lateral Observatory, Mapleton, Utah, United States

Data source: Unknown

Description

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.

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dvdearden
David Dearden
License: None (All rights reserved)
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NGC 7331 and Environs, Deer Lick Galaxy Group and Stephan's Quintet, LRGB, 18-27 Oct 2017, 




    

        David Dearden