Crescent Nebula

From Wikipedia, the free encyclopedia

"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 William 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 citation needed] 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"

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Date : September 2021 & August 2022
Location : Backridge Observatory, Spruce Knob, West Virginia

Equipment used :
 Lens or telescope -- Homemade 16" Newtonian with MPCC
 Mount -- AP 1200
 Camera -- QSI 683wsg with Lodestar 2x guider

Acquistion Software : ACP, MaxIm DL, Focusmax
Processing Software : PixInsight, Photoshop

Exposure Detail : Total hours  3.75   HOO