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Contains:  M 3, NGC 5272
Getting plate-solving status, please wait...
M3, LRGB with lots of Moonlight, 26 Apr 2018, 


            David Dearden
M3, LRGB with lots of Moonlight, 26 Apr 2018

M3, LRGB with lots of Moonlight, 26 Apr 2018

Technical card

Resolution: 2318x1790

Dates:April 26, 2018

ZWO Blue 31 mm: 17x120" (gain: 139.00) -20C bin 1x1
ZWO Green 31 mm: 17x120" (gain: 139.00) -20C bin 1x1
ZWO Luminance 31 mm: 23x120" (gain: 139.00) -20C bin 1x1
ZWO Red 31 mm: 17x120" (gain: 139.00) -20C bin 1x1

Integration: 2.5 hours

Avg. Moon age: 11.19 days

Avg. Moon phase: 86.21% job: 2034249

RA center: 205.581 degrees

DEC center: 28.395 degrees

Pixel scale: 1.719 arcsec/pixel

Orientation: 86.278 degrees

Field radius: 0.699 degrees

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

Data source: Backyard


It seems M3 is always a bit of an afterthought for me; I image it when there’s too much moonlight for galaxies and the Hα nebulas I usually try have not yet risen, and that was the case this time. This image is LRGB, but with a lot less L than intended because my guider didn’t find a guide star and locked on a hot pixel after doing an automated meridian flip. Still, this image is better than my best previous M3 so I’m happy. I usually deconvolute the RGB as well as the L, but in this case deconvoluting the color made the stars look nasty.

Date: 26 Apr 2018
Subject: M3 globular cluster
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 Ic +PHD 2.6.4.dev10 (Win 10 ASCOM)
Camera: ASI1600MM-Cool, -20 °C, Gain 139 Offset 21
Acquisition: Sequence Generator Pro
Exposure: 23x120 L, 17x180 R, 17x180 G, 17x180 B
Stacking: Deep Sky Stacker 4.1.0 (64-bit) dark+flat+bias, κ-σ stacking with κ = 1.5.
Processing: StarTools 1.4.332: Did RGB combination using StarTool’s LRGB module. Binned 2x2 in StarTools. Used StarTools’ “Wipe”, then stretched RGB in StarTools. Binned the L 2x2 in StarTools, wiped, developed, used HDR core reveal, deconvoluted, the used “Track” to denoise. Went with the default colors from StarTools’ color module. Combined L with RGB in Photoshop. Used Astronomy Tools’ increase star color, some additional deep space & space noise reduction, a little unsharp mask, followed by “less crunchy more fuzzy”, AstroFrame.



David Dearden
License: None (All rights reserved)

Sky plot

Sky plot


M3, LRGB with lots of Moonlight, 26 Apr 2018, 


            David Dearden