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Contains:  Triangulum galaxy, M 33, NGC 598
Getting plate-solving status, please wait...
M33, Triangulum Pinwheel Galaxy, LRGB, 27-29 Oct 2017, 


            David Dearden
M33, Triangulum Pinwheel Galaxy, LRGB, 27-29 Oct 2017

M33, Triangulum Pinwheel Galaxy, LRGB, 27-29 Oct 2017

Technical card

Resolution: 4521x3395

Dates:Oct. 27, 2017Oct. 28, 2017

ZWO Blue 31 mm: 30x180" (gain: 198.00) -20C bin 1x1
ZWO Green 31 mm: 30x180" (gain: 198.00) -20C bin 1x1
ZWO Luminance 31 mm: 48x300" (gain: 139.00) -20C bin 1x1
ZWO Luminance 31 mm: 71x180" (gain: 198.00) -20C bin 1x1
ZWO Red 31 mm: 30x180" (gain: 198.00) -20C bin 1x1

Integration: 12.1 hours

Avg. Moon age: 7.45 days

Avg. Moon phase: 50.76% job: 1795832

RA center: 23.502 degrees

DEC center: 30.648 degrees

Pixel scale: 0.860 arcsec/pixel

Orientation: 270.279 degrees

Field radius: 0.675 degrees

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


I’ve always thought M33 is a beautiful galaxy. It’s close enough you can see a lot of what is going on, and it has lots of pretty star-forming regions and clusters of bright young blue stars. This is the first time I’ve been able to pick up some of the faint outer arms, and it was worth it to use the extra integration. After doing most of the acquisition with 180-s subs at a gain of 200, I added more luminance with 300-s subs at unity gain (139 on this camera). The latter are what really picked up the outer arms. I thought about adding some Hα to further enhance the star-forming regions, but after seeing the RGB decided they already show up pretty well. The sky was especially clear for the data that make up this image. Much better than my last previous attempt. This monochrome LRGB stuff is hard (i.e. more fun to process!) but produces nicer results than I was ever able to get with a one-shot color camera.

Date: 27-29 Oct 2017
Subject: M33, Triangulum Pinwheel Galaxy
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 (Win 10 ASCOM) using predictive PEC algorithm
Camera: ASI1600MM-Cool, -20 °C, Gain 198 Offset 50 (with some L done at Gain 139 Offset 21)
Acquisition: Sequence Generator Pro
Exposure: 71x180 L 30x180 R, 30x180 G, 30x180 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. Gradient Xterminator. Several rounds of layer-masked levels to try and get rid of color gradients, followed by several rounds of layer-masked desaturation for the same purpose. Several rounds of “Increase Star Color.” AstroFrame.



David Dearden
License: None (All rights reserved)

Sky plot

Sky plot


M33, Triangulum Pinwheel Galaxy, LRGB, 27-29 Oct 2017, 


            David Dearden