Photo of the Week for November 10, 2017
The aptly named Crescent Nebula, NGC6888, is found roughly 2½ degrees southwest of Gamma Cygni. At the Crescent’s centre is a remarkable, 7.5-magnitude Wolf-Rayet star (WR136) that shines some 250,000 times brighter than our Sun and is 15 times more massive. Wolf-Rayet stars are also characterized by high rates of mass loss—which explains the nebulous cocoon surrounding WR136. To see the Crescent, which is the brighter nebulosity visible along most of the object’s perimeter, you need a dark country sky and a scope equipped with a narrow-band nebula filter.
To capture this remarkably detailed photo of the Crescent Nebula, Nepean, Ontario, imager Oleg Bouevitch used a Celestron Edge HD 11 flat-field Schmidt-Cassegrain telescope (with a 0.7× reducer for an effective focal ratio of f/7) and Atik 383L+ CCD camera to acquire a total of 42, 15-minute exposures shot through Astroden H-alpha, O-III and S-II narrowband filters