Hemisphere:  Northern  ·  Contains:  Coma Pinwheel  ·  IC 781  ·  IC781  ·  M 99  ·  M99  ·  NGC 4254  ·  NGC 4262  ·  NGC 4298  ·  NGC 4302  ·  NGC4262  ·  NGC4298  ·  NGC4302  ·  Virgo Cluster Pinwheel
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NGC 4302, 4298, & 4254 (M99), LRGB, 18-21 Apr 2020, 


            David Dearden
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NGC 4302, 4298, & 4254 (M99), LRGB, 18-21 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: RC Astro GradientXTerminator  ·  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:April 18, 2020April 20, 2020April 21, 2020

ZWO Blue 31 mm: 24x180" (gain: 139.00) -20C bin 1x1
ZWO Green 31 mm: 22x180" (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: 6.3 hours

Avg. Moon age: 26.89 days

Avg. Moon phase: 8.83%

Bortle Dark-Sky Scale: 5.00

Astrometry.net job: 3447967

RA center: 12h 20' 16"

DEC center: +14° 38' 24"

Pixel scale: 1.719 arcsec/pixel

Orientation: 1.214 degrees

Field radius: 0.678 degrees

Resolution: 2208x1780

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

Data source: Backyard


50.2 ± 5.5 MLy (for all 3 prominent galaxies)

It was a real struggle to get this image as clouds played havoc with it. Hence, it took several sessions to get enough data. I was also trying for M83 as a second target on the nights I collected this, and between clouds killing sessions and a mountain in the way I still don’t have anything for that. In processing this image, I tried both my usual workflow, in which I treat the L and the RGB separately, and also combining LRGB and using synthetic luminance from the RGB, processing the whole thing at once. I think my usual workflow gave better results, at least this time, as I tend to process L for sharpness and RGB more for smoothness. There were pretty significant background gradients that my flats did not fix and eventually I ended up using GradientXTerminator for them. The result is a much better image than my previous attempts on these targets (including the fact that I got all of them in one frame this time, which wasn’t possible with my small-chip DSI IIc camera). I notice that the core of NGC 4254 came out looking slightly green, which doesn’t seem quite correct but it’s what my data yielded so I’m reluctant to mess with it. The star colors look reasonable and changing the color balance changes that. I’m never sure about how accurate my colors are (I usually go with what StarTools’ color module gives), but one thing I’m fairly confident of is that the 3 most prominent galaxies in this image have distinctly different colors. I’m guessing that might reflect different average ages of their stellar populations, or perhaps differences in dust content and the accompanying scattering. I didn’t realize NGC 4254 is in the Messier Catalog (M99) until I was looking up distances in Wikipedia!

Date: 18-11 Apr 2020
Subject: NGC 4254, 4298, and 4302
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: 60x180 L, 20x180 R, 22x180 G, 24x180 B
Stacking: Deep Sky Stacker 4.2.3 (64-bit) dark+flat+bias, κ-σ stacking with κ = 1.5
Processing: StarTools 1.6.392 beta: Software binned L 2x2, cropped, wiped, developed, HDR (reveal core), deconvoluted, untrack denoised (grain equalization). Combined R, G, & B in StarTools, accounting for the differences in integration. Software binned 2x2, cropped, wiped, developed, HDR (reveal all), color, untrack denoised (grain removal). Applied L to color in Photoshop. A little bit of levels, one round of deep space noise reduction. AstroFrame.



David Dearden
License: None (All rights reserved)

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NGC 4302, 4298, & 4254 (M99), LRGB, 18-21 Apr 2020, 


            David Dearden