Hemisphere:  Southern  ·  Contains:  M 12  ·  M12  ·  NGC 6218
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M12, LRGB, 19 May 2020, 


            David Dearden
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M12, LRGB, 19 May 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:May 19, 2020

ZWO Blue 31 mm: 15x180" (gain: 139.00) -20C bin 1x1
ZWO Green 31 mm: 15x180" (gain: 139.00) -20C bin 1x1
ZWO Luminance 31 mm: 24x180" (gain: 139.00) -20C bin 1x1
ZWO Red 31 mm: 15x180" (gain: 139.00) -20C bin 1x1

Integration: 3.5 hours

Avg. Moon age: 26.56 days

Avg. Moon phase: 9.66%

Bortle Dark-Sky Scale: 5.00

Astrometry.net job: 3529169

RA center: 16h 47' 16"

DEC center: -1° 56' 45"

Pixel scale: 1.718 arcsec/pixel

Orientation: -177.322 degrees

Field radius: 0.696 degrees

Resolution: 2308x1780

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

Data source: Backyard


15,700 ly

The forecast was a bit iffy (wind and high cloud) but I decided to get my gear out anyway and I’m glad I did as the weather turned out OK. My last attempt on M12 was 4 years ago, and this is a far better image. Wikipedia indicates this globular is more loosely-packed than usual, and has fewer low-mass stars than usual; it is reported to be about 75 ly in diameter. I like the colors it displays, but as usual I’m never too certain that my representation of the colors is accurate, and these are definitely not the same as I got last time with a one-shot-color camera. The star field in this part of the sky is quite dense and rich.

Date: 19 May 2020
Subject: M12
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 2.6.8 (Win 10 ASCOM)
Camera: ASI1600MM-Cool, -20 °C, Gain 139 Offset 21
Acquisition: Sequence Generator Pro
Exposure: 24x180 L, 15x180 R, 15x180 G, 15x180 B
Stacking: Deep Sky Stacker 4.2.3 (64-bit) dark+flat+bias, κ-σ stacking with κ = 1.5
Processing: StarTools 1.6.394RC: Composed L, R, G, & B accounting for total integration times in creating a combined synthetic luminance. Cropped, wiped (vignette), developed (95%), HDR (reveal core), deconvoluted slightly (2 pixels), and untrack denoised. In Photoshop, some levels adjustments to darken the background followed by 1 round of Astronomy Tools’ “less crunchy more fuzzy”. AstroFrame.



David Dearden
License: None (All rights reserved)


  • Final
    M12, LRGB, 19 May 2020, 


            David Dearden
  • M12, LRGB, 19 May 2020, 


            David Dearden


Description: Same processing except used “reveal all” in HDR instead of “reveal DSO core”. This is perhaps a more honest representation of the dynamic range in brightness in the cluster.

Sky plot

Sky plot


M12, LRGB, 19 May 2020, 


            David Dearden