Hemisphere:  Northern  ·  Contains:  IC 4263  ·  IC4263  ·  IC4278  ·  M 51  ·  M51  ·  NGC 5169  ·  NGC 5194  ·  NGC 5195  ·  NGC 5198  ·  NGC5169  ·  NGC5195  ·  NGC5198  ·  Whirlpool galaxy
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M51, Whirlpool Galaxy, LRGB, 26 Feb 2020, 


            David Dearden
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M51, Whirlpool Galaxy, LRGB, 26 Feb 2020

Imaging telescopes or lenses: Astro-Tech AT8IN

Imaging cameras: ZWO ASI1600MM-Cool

Mounts: Skywatcher NEQ-6 Pro Synscan

Guiding telescopes or lenses: Astro-Tech AT8IN

Guiding cameras: ZWO AS120MM-Mini

Focal reducers: High Point Scientific Coma Corrector Photo & Visual For Netwonian Telescopes 2"

Software: DeepSkyStacker  ·  Noel Carboni's Astro Tools for PhotoShop  ·  StarTools  ·  AstroPlanner  ·  PHD2 Guiding  ·  Sequence Generator Pro  ·  EQASCOM  ·  photoshop

Filters: ZWO Red 31 mm  ·  ZWO Luminance 31 mm  ·  ZWO Green 31 mm  ·  ZWO Blue 31 mm

Accessory: Orion Thin Off Axis Guider (TOAG)  ·  Robert Brown's Arduino ASCOM Focuser Pro DIY  ·  ZWO EFW filter wheel

Dates:Feb. 26, 2020

ZWO Blue 31 mm: 50x120" (gain: 139.00) -20C bin 1x1
ZWO Green 31 mm: 41x120" (gain: 139.00) -20C bin 1x1
ZWO Luminance 31 mm: 92x180" (gain: 139.00) -20C bin 1x1
ZWO Red 31 mm: 50x120" (gain: 139.00) -20C bin 1x1

Integration: 9.3 hours

Avg. Moon age: 2.56 days

Avg. Moon phase: 7.26%

Bortle Dark-Sky Scale: 5.00

Astrometry.net job: 3291919

RA center: 13h 29' 49"

DEC center: +47° 11' 40"

Pixel scale: 1.719 arcsec/pixel

Orientation: 88.867 degrees

Field radius: 0.696 degrees

Resolution: 2308x1780

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

Data source: Backyard


23 MLy
M51 is one of my favorite targets and a fitting way to start the 2020 galaxy season. I tried to go a bit deeper than before, with the conflicting goals of picking up the tidal streams and avoiding too much noise in the background. I always seem to struggle with colors for this target, and this attempt was no exception. I kept getting way too much green, even though I took fewer green subframes than red or blue. This image involved using the newest beta of StarTools so I also did a lot of experimenting with new processing modules. Eventually I discovered that if I did not do a wipe on the RGB, the colors came out less intense but a lot better balanced in my opinion. There’s less noise reduction in this image than usual because I used the new “grain equalization” process instead of the older “grain removal.” The new process is definitely faster and I think it generally looks better. Finally, at last I’ve fixed a problem of occasional, intermittent dropped usb connections to my camera that has plagued me for a long time. It turns out it was the usb 3 cable that connected the camera to the usb hub. I also replaced the old usb 2 hub with a new usb 3 hub and so far this has been rock solid. At any rate, this is definitely my best M51 so far.

Date: 26 Feb 2020
Subject: M51, Whirlpool 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 + ASI120MM-mini +PHD 2.6.7 (Win 10 ASCOM)
Camera: ASI1600MM-Cool, -20 °C, Gain 139 Offset 21
Acquisition: Sequence Generator Pro
Exposure: 92x180 L, 50x120 R, 41x120 G, 50x120 B
Stacking: Deep Sky Stacker 4.2.3 (64-bit) dark+flat+bias, κ-σ stacking with κ = 1.5.
Processing: StarTools 1.6.387: For L, software binned 2x2, cropped, wiped, developed, HDR optimized “soft”, deconvoluted, and untrack denoised (grain equalization). Combined R, G, & B in StarTools, accounting for exposure total times in combination. 2x2 software binned, cropped, developed, HDR optimized “reveal all,” color module with some saturation boost. Untrack denoised (grain elimination). In Photoshop, did some layer-masked levels work to clean up the stacked L data, then applied L as luminance layer at 100% opacity. Did a bit of saturation boosting and a bit more levels adjustment. AstroFrame.



David Dearden
License: None (All rights reserved)

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M51, Whirlpool Galaxy, LRGB, 26 Feb 2020, 


            David Dearden