Great Hercules Cluster (M13)

Object Type: Globular Cluster
Top image - AP 5" Refractor, 90 min; Bottom image - C-9.25" SCT, 30 min.

Messier 13 (NGC 6205), the Great Globular Cluster in Hercules, is the finest globular cluster in the northern sky, discovered by Edmond Halley in 1714 and catalogued by Messier in 1764. It lies about 22,000-25,000 light-years away and packs several hundred thousand stars into a ball roughly 145 light-years across. At magnitude 5.8 it is faintly visible to the naked eye and spectacular in a telescope. In 1974 the famous 'Arecibo message,' humanity's first deliberate interstellar radio broadcast, was aimed toward M13. The small galaxy NGC 6207 lies nearby in the same field.