M-55 (NGC-6809) is a large, loosely structured globular star cluster located in the constellation of Sagittarius. It is relatively close to Earth, lying only 18,000 light years distant. It is 90 light years in diameter. M-55 was discovered by Lacaille in 1752, and later added to Charles Messier's catalog as number 55. It is estimated to be 12 billion years old.
This image, acquired on September 10, 2012, is a 15 minute integration of 50 second exposures through the Celestron C-11 at f/2, using the HyperStar III imaging system and the Starlight Express SXVR-H694C color CCD camera, operating at -10 degrees below ambient temperature and binned 1 X 1. Guided, captured and combined using Maxim DL5 Pro. Post processed using PhotoShop CS2, Gradient XTerminator, StarShrink, Carboni's Astro Tools and NoiseWare.