by Bob Franke
Taken from 6/19/2010 to 8/5/2010 in Chino Valley, AZ
RCOS 12.5" Ritchey-Chrétien w/ an SBIG STL-11000 camera using Astrodon filters
Exposure Details:
Ha 600 min. (20 x 30 min)
OIII 660 min. (22 x 30 min)
RGB 225 min. ( 5 x 15 min each)
North is to top.
NGC 6888, the Crescent Nebula, is located the constellation Cygnus at a distance of about 5,000 light-years. The nebula is created by the bright central star, HD 192163. About 400,000 years ago, the star ejected material, when it became a red giant. Then, about 150,000 years later, HD 192163 shed its outer envelope into a strong stellar wind, and became a Wolf-Rayet star (WR 136). The second explosion eventually over took the previous ejected gas. This collision formed and lit up the nebula we see today. Wr 136 is expected to end its life with a supernova explosion, sometime in the next million years.
This synthetic color image was created by mapping Ha data to red and OIII filtered data to green and blue. This creates an image with hydrogen gas shown as red and doubly ionized oxygen is teal. Additionally, an RGB layer was added for star colors.