Hemisphere:  Northern  ·  Constellation: Coma Berenices (Com)  ·  Contains:  NGC 4712  ·  NGC 4725  ·  NGC 4747  ·  NGC4712  ·  NGC4725  ·  NGC4747
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NGC 4725 in the Coma I Group, LRGB, 4 Apr 2020, 


            David Dearden
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NGC 4725 in the Coma I Group, LRGB, 4 Apr 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: photoshop  ·  DeepSkyStacker  ·  Noel Carboni's Astro Tools for PhotoShop  ·  StarTools  ·  AstroPlanner  ·  PHD2 Guiding  ·  Sequence Generator Pro  ·  Cartes du Ciel  ·  EQASCOM

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:April 3, 2020April 4, 2020

ZWO Blue 31 mm: 20x180" (gain: 139.00) -20C bin 1x1
ZWO Green 31 mm: 20x10" (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: 5.1 hours

Avg. Moon age: 10.06 days

Avg. Moon phase: 76.83%

Bortle Dark-Sky Scale: 5.00

Astrometry.net job: 3387145

RA center: 12h 50' 43"

DEC center: +25° 37' 43"

Pixel scale: 1.719 arcsec/pixel

Orientation: -179.059 degrees

Field radius: 0.682 degrees

Resolution: 2268x1740

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

Data source: Backyard


40 ± 6 MLy

I had a clear night that enabled me to capture C/2019 Y4 ATLAS, but as the Moon sank lower this target presented itself; my last try was in 2016 so I was sure I could do better than then. This galaxy has one of the more interesting shapes I’ve observed, a single spiral arm extending from a more central ring. This really looks like a tidal stream to me. The smaller galaxy to the lower right, NGC 4747, also has a nice tidal stream; it almost looks like a cosmic skid mark on the sky. There was a goodly amount of background sky fog in this image, which I have mostly darkened out. I haven’t compared with enough other images to decide whether or not it might be real.

Date: 3-4 Apr 2020
Subject: NGC 4725 and vicinity
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: 20x180 R, 20x180 G, 60x180 L, 20x180 B
Stacking: Deep Sky Stacker 4.2.3 (64-bit) dark+flat+bias, κ-σ stacking with κ = 1.5 (see above!).
Processing: StarTools 1.6.392 beta: Software binned L 2x2, cropped, wiped, developed, HDR (reveal all), untrack denoised (grain equalization). Combined R, G, & B in StarTools. Software binned L 2x2, cropped, wiped, developed, HDR (reveal all), color with a lot of saturation boost, untrack denoised (grain removal). Applied L to color in Photoshop. Several rounds of levels and curves, and several of deep space noise reduction. AstroFrame.


Sky plot

Sky plot


NGC 4725 in the Coma I Group, LRGB, 4 Apr 2020, 


            David Dearden