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 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.
Telescope : SW Esprit 100ED
Mount : SW EQ6-ri
Camera : ZWO 533 mc pro
Guiding : 8x50 SW finder with QHY 5IIL
Filters: Total exposure time : 9 hours with differnts exposures(300, 600sec.) , L-enchance 1.25.
Programs I have used : Nina 2.2 _ PixInsight 1.8.9-1
Location: Grammatiko, Attiki