M13 is found in the constellation Hercules. Consisting of probably a million stars at a distance of 21,000 light years it is easily discernable in binoculars. First noted by Halley in 1714: “This is but a little Patch, but it shews it self to the naked Eye, when the Sky is serene and the Moon absent”.
Messier added it to his catalog in 1764. Messier noted: “In the night of June 1 to 2, 1764, I have discovered a nebula in the girdle of Hercules, of which I am sure it doesn’t contain any star; having examined it with a Newtonian telescope of four feet and a half [FL], which magnified 60 times, it is round, beautiful & brilliant, the center brighter than the borders”.
Determination of it’s true nature had to wait until the Herschels examined it with their improved telescopes of the 1780s. May 16, 1787. 20 feet telescope. “The 13th of the Connoiss. [M 13 = NGC 6205] is a most beautiful cluster of stars. It is exceedingly compressed in the middle and very rich. The most compressed part of it is round and is about 2 or 2 1/2? in diameter, the scattered stars which belong to it extend to 8 or 9? in diameter, but are irregular.”
The image is a stack of eight 2 minute exposures at ISO 1600 with a Canon 350D and 0.63 FL reducer on the club Celestron 9.25″.