NGC 6888 – Crescent Nebula, HA+RGB

Location of photo
Petrova gora and Zagreb, Croatia
Date/Time of photo
Optics: SW ED80/FF x0.85 Camera: Qhy8 color Mount and guidng: NEQ6 Pro, SW 9x50 finderguider Guding camera: Qhy5 IIc Exposure: 4x15 min RGB , 21x15 min HA Software: PHD2, Nebulosity, Pixinsight 1.8, PS CS6
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 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. This image is a composite of 21x900 sec of hydrogen alpha and 4x900 sec of RGB.
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