M4 (NGC 6121)
Messier 4 (NGC 6121) is a globular cluster located in the constellation Scorpius, in the Galactic Center of the Milky Way Galaxy in the Local Group of galaxies. M4 is 7,200 light years away from Earth.
M4 is best viewed during mid-summer, is magnitude 5.9, and can be viewed with naked eye (barely). M4 is 26' 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.