Messier 13 or M13 (also designated NGC 6205 and sometimes called the Great Globular Cluster in Hercules or the Hercules Globular Cluster) is a globular cluster in the constellation of Hercules.

With an apparent magnitude of 5.8, it is barely visible with the naked eye on a very clear night. Its diameter is about 23 arc minutes and it is readily viewable in small telescopes. Nearby is NGC 6207, a 12th magnitude edge-on galaxy that lies 28 arc minutes directly north east. A small galaxy, IC 4617, lies halfway between NGC 6207 and M13, north-northeast of the large globular's center.

Source: wikipedia