This is a 30-minute exposure taken with an SBIG STL-1301E CCD camera through Kopernik's 20 inch F/8.1 telescope. The field of view is about 13 x 15 arc minutes, with North at the top.
Charles Messier (Oct 18th, 1780): '''Nebula without star between Sagittarius and the head of Capricorn…."
William Herschel (1774): ''(resolved into stars) A miniature of M-3 (another globular star cluster), and pale to the gaze."
Quote from K. G. Jones': Messier's Nebulae & Star Clusters:
"A slight mottling of the edges was all that could be detected of its globular identity in an 8-inch telescope using a power of 120x………."
M-75 (NGC 6864) is a globular star cluster in the Constellation of Sagittarius. Messier's friend Pierre Méchain discovered it in August 1780. M-75 is at a distance of about 67,500 light years and its apparent size on the sky translates to a true radius of some 67 light years. M-75 is the most distant of Messier's star clusters and is one of the more densely concentrated globular clusters known. The absolute magnitude of M75 is about -8.5 or some 180,000 times more luminous than the Sun..
(Click here for the latest news on Globular Star Cluster distances and ages!!)
George Normandin, KAS
June 18th, 2007