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Contains:  Sombrero galaxy, M 104, NGC 4594
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M104, Sombrero Galaxy, LRGB, 21-22 Apr 2018, 


            David Dearden
M104, Sombrero Galaxy, LRGB, 21-22 Apr 2018

M104, Sombrero Galaxy, LRGB, 21-22 Apr 2018

Technical card

Resolution: 2312x1793

Dates:April 21, 2018

ZWO Blue 31 mm: 19x180" (gain: 139.00) -20C bin 1x1
ZWO Green 31 mm: 11x180" (gain: 139.00) -20C bin 1x1
ZWO Luminance 31 mm: 48x180" (gain: 139.00) -20C bin 1x1
ZWO Red 31 mm: 21x180" (gain: 139.00) -20C bin 1x1

Integration: 4.9 hours

Avg. Moon age: 5.86 days

Avg. Moon phase: 34.10% job: 2027443

RA center: 189.971 degrees

DEC center: -11.634 degrees

Pixel scale: 1.719 arcsec/pixel

Orientation: 353.910 degrees

Field radius: 0.698 degrees

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

Data source: Backyard


I had hoped to pick up a little bit of the internal structure of the Sombrero Galaxy in this year’s attempt, but despite very nice sky conditions my guiding wasn’t great so neither was the internal detail, at least in my hands. I only stacked the best 80% of the luminance data hoping that would sharpen things up a bit (and I think it did, a bit). Nevertheless, this galaxy really stands out against the surrounding star field without any special processing to make it do so. I struggled a bit with the color choice; depending on where I sampled the image, I could either get the reddish version I eventually went with or one that was more bluish. I saw examples of both on Astrobin, but decided the redder version was probably closer to “true” color and it definitely gave more color to the stars. I had a lot less green data than I had planned because an unexpected neighbor’s tree got in the way before my session ended, but I judged it sufficient and processed what I had. I’m continuing to enjoy 64-bit Deep Sky Stacker 4.1.0. I’ve learned the trick of registering everything using the best luminance sub as reference and cropping the luminance and RGB the same to make the final LRGB combination quite easy.

Date: 21-22 Apr 2018
Subject: M104, Sombrero 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 + DSI Ic +PHD 2.6.4.dev10 (Win 10 ASCOM)
Camera: ASI1600MM-Cool, -20 °C, Gain 139 Offset 21
Acquisition: Sequence Generator Pro
Exposure: 48x180 L, 21x180 R, 11x180 G, 19x180 B
Stacking: Deep Sky Stacker 4.1.0 (64-bit) dark+flat+bias, κ-σ stacking with κ = 1.5.
Processing: StarTools 1.4.332: Did RGB combination using StarTool’s LRGB module. Binned 2x2 in StarTools. Used StarTools’ “Wipe”, then aggressively stretched and deconvoluted L and RGB separately in StarTools. Sampled the color in the halo around M104 to get the colors I went with. Combined L with RGB in Photoshop. Used Astronomy Tools’ increase star color, some additional deep space & space noise reduction, followed by “less crunchy more fuzzy”, AstroFrame.



David Dearden
License: None (All rights reserved)

Sky plot

Sky plot


M104, Sombrero Galaxy, LRGB, 21-22 Apr 2018, 


            David Dearden