M 21, NGC 6531
Object: Open Cluster
Constellation: Sagittarius
Apparent Magnitude: 6.5
Est. Distance: 4250 ly
Telescope: Celestron CPC 800 (8")
Camera: Nikon D70 unmodified
Exposure: 1x30 sec (0.5 mins)
ISO: 1600
Date: 2nd June 2008
Wikipedia link
Annotated Version