Messier 13 - Hercules Nebula
Discovered by Edmond Halley, of Halley's comet fame, in 1714. Cataloged years later by Charles Messier in 1764, Messier thought no stars existed in this object. In 1779 individual stars were resolved. Today M13 consists of over 100,000 stars making it one of the most prominent star clusters in the Northern Hemisphere.
Messier 13 is more than 25,000 light years from earth and is visible in the summer months.