NGC 7023, Iris Nebula, LRGB, 24-26 Aug 2017 (David Dearden)

NGC 7023, Iris Nebula, LRGB, 24-26 Aug 2017

The Iris Nebula is another favorite target, but I noticed I have not attempted it since 2014, so I’m overdue. I tried a few test Hα and OIII subs, but didn’t see much and decided LRGB would be best here. I tried to get a lot of subs for luminance; I probably needed a few more RGB. I had some challenges with the auto-centering in Sequence Generator Pro (it does great for large adjustments, but when trying to get within the last few hundred pixels it doesn’t seem to move the mount much; I need to do some research and figure out what is wrong). Anyway, as a result I had to crop out a lot more stacking artifacts than usual. Nevertheless, I like how this image turned out as it is way better than my previous best for the Iris. I’m struck by how far out the nebula extends and by the dark regions blocking the background stars.

Date: 24-26 Aug 2017

Subject: NGC 7023, Iris Nebula

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 2.6.3.7 (Win 10 ASCOM) using predictive PEC algorithm

Camera: ASI1600MM-Cool, -20 °C, Gain 139 Offset 21

Acquisition: Sequence Generator Pro 2.6.0.24

Exposure: 12x300 R, 14x300 G, 12x300 B, 78x300 L

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, 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. Did deep space and space noise reduction in the L. Added L as luminance to the RGB, did a little local contrast enhancement, a slight tweak of saturation, and less crunchy more fuzzy. AstroFrame.

ZWO ASI1600MM/QHY163M

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Status	Advanced success
Started	...
Astrometry.net job	1704752
PixInsight job	BJW0WYKARIM16C5ICVGNZGCB91J1ZDVT
PixInsight queue size	n/a
PixInsight stage	n/a

RA (center)	21h01m42s.600
RA (top/left)	21h07m16s.610
RA (top/right)	20h56m33s.959
RA (bottom/right)	20h56m17s.700
RA (bottom/left)	21h06m39s.249

Dec (center)	+68°10′19″.19
Dec (top/left)	+68°30′25″.16
Dec (top/right)	+68°33′54″.62
Dec (bottom/right)	+67°49′33″.53
Dec (bottom/left)	+67°46′14″.27

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