|
The Crescent Nebula, also cataloged as NGC 6888 and as Caldwell 27, is an expanding shell of hydrogen gas measuring 16 x 25 light years across in the constellation Cygnus. The name "crescent" is evoked by its ethereal glow in the shape of a young moon, when viewed through large backyard telescopes. The red glowing hydrogen gas is illuminated by the central brilliant Wolf-Rayet star. Wolf-Rayet stars shed huge quantities of material, which can collide with hydrogen gases that previously constituted the star's outer atmosphere. A similar process creates the spectacular Bubble Nebula, which I have imaged as both a wide-angle view from my backyard and in closer detail at the Hidden Lake Observatory.
The image above was obtained with an ST2000XM camera through a TEC 140mm refractor. The image combines 140 minutes of Hydrogen-alpha, 90 minutes of red, 60 minutes of green, and 80 minutes of blue exposures. The red channel was combined with the H-alpha exposures for luminance weighted about 70%. Total exposure time was over 6 hours.
For the image below, take 4 years earlier from my backyard, two hours of imaging with an ST10-XME camera through a Celestron C8 and a 0.67x reducer was utilized. The luminance of 13x5-minute exposures in H-alpha were blended with 3x5 minute exposures through a red filter to create the red channel. Three green and five blue 5 minute exposures completed the set. |
|
