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 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.
Telescope: APM Astrograph 107, f/6.5 with Baader Steeltrack Focuser and 2.5'' TS FF
Mount: NEQ6 Pro with EQ Mod and XBOX Wireless Controller
Camera: ATIK 314L+
Image Scale: 1.91 arcsec/pixel
Filter: Baader Ha 7nm, OIII 8.5nm, RGB, IDAS LPS
Filter Wheel: Starlight Xpress Motor USB, 7x1.25''
Guide Camera: QHY5 with PHD Guiding and TS UV/IR Block
Guide Scope: Skywatcher Finderscope 8x50
Exp. Time: 5 hours & 12 mins (Ha: 150 min, O3: 72 min, R,G,B: 30,30,30 min)
Temperature: Ambient (8C..14C), CCD (-5..-10C)
Capture: Nebulosity 2.3.0
Register, Stack: Maxim DL, CCD Stack
Processing: Photoshop CS3
Date: 13 May 2011 (Ag. Panteleiomon, Attica, GR) & 29 July 2011 (Parnon Mount, Arcadia, GR)
NGC 6888 - Crescent Nebula Wiki
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