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Contains:  Omega nebula, M 17, NGC 6618
Getting plate-solving status, please wait...
M17, Omega (Swan, Lobster) Nebula, HαRRGB, 3-4 July 2018, 


            David Dearden
M17, Omega (Swan, Lobster) Nebula, HαRRGB, 3-4 July 2018

M17, Omega (Swan, Lobster) Nebula, HαRRGB, 3-4 July 2018

Technical card

Resolution: 2328x1800

Dates:July 3, 2018July 4, 2018

ZWO Blue 31 mm: 15x180" (gain: 139.00) -20C bin 1x1
ZWO Green 31 mm: 15x180" (gain: 139.00) -20C bin 1x1
ZWO H-alpha 7nm: 29x300" (gain: 139.00) -20C bin 1x1
ZWO Red 31 mm: 15x180" (gain: 139.00) -20C bin 1x1

Integration: 4.7 hours

Avg. Moon age: 19.97 days

Avg. Moon phase: 72.24% job: 2130278

RA center: 275.137 degrees

DEC center: -16.173 degrees

Pixel scale: 1.719 arcsec/pixel

Orientation: 269.461 degrees

Field radius: 0.703 degrees

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

Data source: Backyard


I probably could have given more integration time to this, and would like to get SII and OIII for a Hubble palette version, but was very impressed with the Hα so decided to process with that. I got 20 subs of R, G, and B, but let Deep Sky Stacker pick the best 75% of each for stacking. I also reviewed the Starizona HαRRGB methods and attempted to follow them, with a result that looks much better to me than some of my other recent attempts where I tried to blend in more Hα (Now I probably need to go back and reprocess some of those with these methods—always something more to try!). I’ve been torn about which version I like better. Starizona method 1 gives an image with more stars (OK, it wasn’t “pure” method 1 because I screen layered the RGB stars back on top of the image) and less nebulosity. Ultimately I think I like it better. Method 2 shows off the nebulosity better, but the stars don’t look as good in my opinion and there’s a bit of an overall pink-reddish cast to it. So I’ll post both versions, but let the “method 1” version be the “final.” The guiding wasn’t great, so my stars are a little more “eggy” than usual.

Date: 3-4 Jul 2018
Subject: M17, Omega (Swan, Lobster) Nebula
Scope: AT8IN+High Point Scientific Coma Corrector
Filters: ZWO 31 mm diameter unmounted R, G, B, Hα
Mount: EQ-6 (EQMOD 2.000j)+PEC
Guiding: Orion Thin Off-axis Guider + DSI IIc +PHD 2.6.5 (Win 10 ASCOM)
Camera: ASI1600MM-Cool, -20 °C, Gain 139 Offset 21
Acquisition: Sequence Generator Pro
Exposure: 15x180 R, 15x180 G, 15x180 B, 29x300 Hα
Stacking: Deep Sky Stacker 4.1.1 (64-bit) dark+flat+bias, κ-σ stacking with κ = 1.5. Selectively stacked only the best 75% of RGB
Processing: StarTools 1.4.332: Combined R, G, and B in StarTools. Binned 2x2, cropped, developed, HDR, color, deconvolution. Stopped tracking to smooth. Binned Hα 2x2, cropped, vignette wiped, and developed followed by HDR (core reveal). Deconvolution followed by untrack smoothing. Combined Hα with RGB in Photoshop using either Starizona method 1 or Starizona method 2 (google it). Screen layered RGB stars (extracted from RGB using StarTools) on top of the method 1 image, followed by a few rounds of “decrease star size” and layer-masked “less crunchy more fuzzy.” AstroFrame.



David Dearden
License: None (All rights reserved)


  • M17, Omega (Swan, Lobster) Nebula, HαRRGB, 3-4 July 2018, 


            David Dearden
  • Final
    M17, Omega (Swan, Lobster) Nebula, HαRRGB, 3-4 July 2018, 


            David Dearden


Starizona method 1

Sky plot

Sky plot


M17, Omega (Swan, Lobster) Nebula, HαRRGB, 3-4 July 2018, 


            David Dearden