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Abell 2151, Hercules Galaxy Cluster, LRGB, 13-15 May 2019, 


            David Dearden
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Abell 2151, Hercules Galaxy Cluster, LRGB, 13-15 May 2019

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: RC Astro GradientXTerminator  ·  DeepSkyStacker  ·  Silicon Fields StarTools 1.3  ·  Noel Carboni's Astro Tools for PhotoShop  ·  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:May 13, 2019May 14, 2019May 15, 2019

ZWO Blue 31 mm: 20x180" (gain: 139.00) -20C bin 1x1
ZWO Green 31 mm: 30x180" (gain: 139.00) -20C bin 1x1
ZWO Luminance 31 mm: 60x180" (gain: 139.00) -20C bin 1x1
ZWO Red 31 mm: 20x180" (gain: 139.00) -20C bin 1x1

Integration: 6.5 hours

Avg. Moon age: 10.05 days

Avg. Moon phase: 76.43%

Bortle Dark-Sky Scale: 5.00

Astrometry.net job: 2712644

RA center: 16h 5' 15"

DEC center: +17° 56' 30"

Pixel scale: 1.719 arcsec/pixel

Orientation: -176.769 degrees

Field radius: 0.699 degrees

Resolution: 2318x1790

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

Data source: Backyard


I was sure the AT8IN would do a better job on this cluster than the ST80 with a focal reducer did on my last attempt, and my Newtonian did come through. I had a bit more moonlight than I like for LRGB imaging, but bad weather is coming and this target was well placed. There are a huge number of faint fuzzies in this part of the sky, and this cluster is about 500 million light years away! This is currently the most distant target in my collection. The final result came out of StarTools’ color module with a lot of red, but I hesitate to arbitrarily mess very much with the color balance; I guess I need to learn some good techniques for properly adjusting it. I vacillated between the reddish and bluer versions, and I guess I’ll post both and seek opinions about which is better!

Date: 13, 14, 15 May 2019
Subject: Abell 2151, Hercules Galaxy Cluster
Scope: AT8IN+High Point Scientific Coma Corrector
Filters: ZWO 31 mm diameter unmounted 7 nm L, R, G, B
Mount: EQ-6 (EQMOD 2.000j)+PEC
Guiding: Orion Thin Off-axis Guider + ASI120MM-mini +PHD 2.6.5dev6 (Win 10 ASCOM)
Camera: ASI1600MM-Cool, -20 °C, Gain 139 Offset 21
Acquisition: Sequence Generator Pro
Exposure: 60x180 L, 20x180 R, 30x180 G, 20x180 B
Stacking: Deep Sky Stacker 4.1.1 (64-bit) dark+flat+bias, κ-σ stacking with κ = 1.5.
Processing: StarTools 1.4.341: Cropped, wiped, developed, HDR optimized, deconvoluted, and untrack denoised the L data. Combined RGB in StarTools, cropped, wiped, developed, and used the color module on the RGB data, increasing the saturation. Untrack denoised. Combined L with RGB, performed deep space noise reduction, used several rounds of GradientXTerminator. One round of “less crunchy more fuzzy.” Used a couple of rounds of curves and levels to bring up faint objects, then used layer masked levels to deal with the background without losing them. AstroFrame.



David Dearden
License: None (All rights reserved)


  • Abell 2151, Hercules Galaxy Cluster, LRGB, 13-15 May 2019, 


            David Dearden
  • Abell 2151, Hercules Galaxy Cluster, LRGB, 13-15 May 2019, 


            David Dearden
  • Final
    Abell 2151, Hercules Galaxy Cluster, LRGB, 13-15 May 2019, 


            David Dearden


Description: This is the "bluer" version. I'm not sure which I like better, and would welcome suggestions/comments.


Description: Here's an attempt to avoid clipping the black point. This one is much less processed than the other two versions, and maybe I like it best.

Sky plot

Sky plot


Abell 2151, Hercules Galaxy Cluster, LRGB, 13-15 May 2019, 


            David Dearden