At first glance this looks like a classic globular cluster full of ageing red stars, but along with Berkeley 17 (see October 23rd blog post) NGC 6791, located in the constellation Lyra, is considered to be one of the oldest open clusters in the Milky Way at somewhere around 8 billion years old.
The cluster was first recognized by Friedrich August Theodor Winnecke working at Gottingen University with a 3″ Merz refractor in 1853 and contains approximately 3000 stars. Unusually for open clusters of this age NGC 6791 contains a high number of metal rich stars (principally iron) and a curious set of faint white dwarf stars with differing ages that have been the subject of recent study using the Hubble Telescope.
Imaged on 29/9/2011 6.16am New Mexico using GRAS 3 (TAK TOA 150/FLI ML8300 one shot colour camera. Bin 1). RA: 19h 20m 53.0s DEC: 37° 46′ 18″ (J2000) 20 minutes exposure @ 2 x 600 seconds.