Other Names: Caldwell 27
Optics: Borg Astrograph 101ED at f/4.1
Mount: Atlas EQG using The Sky6 and EQMOD
Camera: Canon EOS 50D [ UV/IR filter modification by Hap Griffin ]
Filters: IDAS Light Pollution Suppression (LPS) Filter
Exposure: 75 Mins [15 x 300s at ISO 800]
Accessories: Auto guided with Borg 45ED and Orion Starshoot Auto guider using PHD
Location: Cypress Hills, SK
Date: August 10, 2010
Notes: Processing: Image acquisition with Maxim DSLR. Image calibration, align, and combine in Maxim DSLR. Levels, curves, crop and resize in Photoshop.
Calibrated w/40 Darks, 40 Bias, 20 Flats using light box, Ambient temperature was +11C

The Crescent Nebula (NGC 6888 or Caldwell 27) is an emission nebula in the Cygnus constellation, 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.