Date Taken: 9/2/2009
Equipment: 5" Televue Telescope with SBIG 10XME camera;
Exposures: GB-13 min each, Ha-23, Lum-9 min. Processing: MaximDL and Photoshop
Crescent Nebula (also NGC 6888 or Caldwell 27) - 5,000 light years away in Cygnus. 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 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.