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Starless NGC 6888 Crescent Nebula in BiColor Ha & OIII

Technical card

Resolution: 3818x3061

Dates: June 2, 2017July 4, 2018July 8, 2018

Astrodon Ha 5nm: 111x240" (gain: 139.00) -20C bin 1x1
Astrodon OIII 3nm: 94x240" (gain: 139.00) -20C bin 1x1
Astrodon OIII 3nm: 54x120" (gain: 201.00) -20C bin 1x1

Integration: 15.5 hours

Darks: ~50

Flats: ~50

Bias: ~250

Avg. Moon age: 17.70 days

Avg. Moon phase: 51.83%

Bortle Dark-Sky Scale: 6.33 job: 2163171

Locations: Backyard Red Zone Observatory, Taylor, MI, Michigan, United States

Data source: Backyard


This is the most challenging starless deep space object I have ever worked on. There were so many stars and artifacts to remove. This also also represents one of the most collected OIII data I have seen on Astrobin resulting in a tremendous amount of detail. Enjoy!

The Crescent Nebula (also known as NGC 6888, Caldwell 27, Sharpless 105) is an emission nebula in the constellation Cygnus, about 5000 light-years away from Earth. It was discovered by Friedrich Wilhelm Herschel in 1792. It is formed by the fast stellar wind from the Wolf-Rayet star WR 136 (HD 192163) colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 250,000 to 400,000 years ago. The result of the collision is a shell and two shock waves, one moving outward and one moving inward. The inward moving shock wave heats the stellar wind to X-ray-emitting temperatures.

It is a rather faint object located about 2 degrees SW of Sadr. For most telescopes it requires a UHC or OIII filter to see. Under favorable circumstances a telescope as small as 8 cm (with filter) can see its nebulosity. Larger telescopes (20 cm or more) reveal the crescent or a Euro sign shape which makes some to call it the "Euro sign nebula".



Douglas J Struble
License: None (All rights reserved)


Starless NGC 6888 Crescent Nebula in BiColor Ha & OIII, 


        Douglas J Struble