M6 (NGC 6405) - Butterfly Cluster
Messier 6 (NGC 6405), also known as the Butterfly Cluster, is an open cluster located in the constellation Scorpius, in the Orion Arm of the Milky Way Galaxy in the Local Group of galaxies. M6 is 1,600 light years away from Earth.
M6 is best viewed during mid-summer, is magnitude 4.2, and can be viewed with naked eye. M6 is 25' in apparent size. For reference, the full moon is 30' (arc minutes) in size.
* The naked eye can see up to magnitude 8 objects under ideal dark sky conditions.