Hemisphere:  Southern  ·  Contains:  Checkmark Nebula  ·  IC 4706  ·  IC 4707  ·  Lobster Nebula  ·  M 17  ·  M17  ·  NGC 6596  ·  NGC 6618  ·  NGC6596  ·  Omega nebula  ·  PGC202343  ·  PGC202348  ·  PGC202351  ·  PGC202400  ·  PGC202401  ·  PGC202409  ·  PGC202437  ·  PGC202443  ·  Sh2-45  ·  Sh2-47  ·  Swan Nebula  ·  omega Nebula
Getting plate-solving status, please wait...


            Gary Imm


            Gary Imm


Imaging telescopes or lenses: Takahashi TOA-130NFB

Imaging cameras: ZWO ASI6200MM Pro

Mounts: Astro-Physics Mach1GTO

Guiding cameras: ZWO ASI174MM

Software: Pixinsight  ·  Main Sequence Software Sequence Generator Pro  ·  Stark Labs PHD2 2.6.3

Filters: Chroma Red 2" unmounted  ·  Chroma SII 3nm  ·  Chroma OIII 3nm  ·  Chroma Ha 3nm  ·  Chroma Blue 2" unmounted  ·  Chroma Green 2" unmounted

Accessory: ZWO M68 OAG  ·  ZWO EFW 2″X7  ·  Takahashi Flattener TOA-67  ·  Feathertouch Focuser Boss II Electronic Focusing Control

Dates:Aug. 14, 2020Aug. 17, 2020Aug. 18, 2020Aug. 19, 2020

Chroma Blue 2" unmounted: 30x120" (gain: 0.00) -5C bin 1x1
Chroma Green 2" unmounted: 30x120" (gain: 0.00) -5C bin 1x1
Chroma Ha 3nm: 24x300" (gain: 100.00) -5C bin 1x1
Chroma OIII 3nm: 24x300" (gain: 100.00) -5C bin 1x1
Chroma Red 2" unmounted: 30x120" (gain: 0.00) -5C bin 1x1
Chroma SII 3nm: 24x300" (gain: 100.00) -5C bin 1x1

Integration: 9.0 hours

Avg. Moon age: 20.46 days

Avg. Moon phase: 6.98%

Astrometry.net job: 3875243

RA center: 18h 21' 5"

DEC center: -16° 10' 46"

Pixel scale: 0.773 arcsec/pixel

Orientation: -1.162 degrees

Field radius: 1.155 degrees

Resolution: 8820x6163

Locations: Backyard (Mag 20.8 - Bortle 4.5), Onalaska, Texas, United States

Data source: Backyard


This object is an emission nebula located 5000 light years away in the constellation of Sagittarius at a declination of -16 degrees.

Of all of the sky objects, I believe that this one has the highest number of commonly accepted nicknames. Focusing on the bright central portion of the nebula leads to the names of the Swan Nebula as well as the Checkmark Nebula. Focusing on the broader nebula leads to the names of the Omega Nebula as well as the Horseshoe Nebula. Which name to use? As in most decisions I make in life, I relied on the internet. The Omega Nebula was the "winner" with 100,000 search engine matches of that name, compared to 65,000 for the Swan Nebula, 15,000 for the Checkmark Nebula, and 10,000 for the Horseshoe Nebula. The Omega Nebula name originated with the famous astronomer John Herschel, who stated that "The figure of this nebula is nearly that of the Greek capital Omega, somewhat distorted and very unequally bright."

Regardless of the name chosen, this nebula is beautiful and fascinating. Thick dust clouds are both obscuring the central bright stars of the nebula and also reflecting and spreading light of other stars. The object spans a big section of the sky — its gas and dust clouds measure about 15 light-years across. This nebula is considered one of the brightest and most massive star-forming regions of our galaxy.

Like the variety of nicknames for this object, I find more different narrowband palette interpretations of this object than any other. I think that this is due to the fairly even signal levels across each channel and the high central brightnesses. This makes it is a tough one to process for an interesting end result, which I think leads to a lot of experimentation and different looks.



Gary Imm
License: Attribution-NonCommercial Creative Commons


  • Final


            Gary Imm
  • M17, 


            Gary Imm


Description: Astrobin Mouseover

Sky plot

Sky plot




            Gary Imm