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NGC6888 / Crescent Nebula 

Classification: Emission nebula, NGC 6888, Caldwell 27, Sh2-105
Constellation: Cygnus (CYG)
Object Location: Ra 20h 12m 40s Dec +38° 24’24° (current)
Size & Distance: 18 x 12, Apx 5000 light years

Date & Location: 09-27-2014 Palomar Mountain, CA.
Exposure: HaOlllOlll, Ha= R, 4 @ 15m, HaOlll=G, Olll=B, 6 @ 15m, all (bin 1x1)
Optics: Telescope Engineering Company APO180FL @ f/5.23 using an Astro-Physics TCC160 F/L 941mm
Mount: Astro-Physics 1200 GTO / ATS 10x36 Pier
Camera: FLI-ML6303E @-20c / CFW2-7 / FLI-Atlas focuser / Guided by SBIG ST-I, w /OAG. FOV 67.5x101.4
Filters: Astrodon 3nm Ha, Olll
Software: MaxImDL 6.06, Photoshop CS5, Topaz Lab

Notes: Sky conditions: Average seeing, calm winds, Temp 65°
Image Field of view is 68 x 101 arc-min.
Look close, bottom right, you can see Soap Bubble Nebula.


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. 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.