M13, also designated NGC 6205, is located in the constellation Hercules. It is commonly called "The Great Cluster in Hercules," and is one of the largest globular cluster's in the night sky.  M13 was discovered by Edmond Halley in 1714, and catalogued by Charles Messier on June 1, 1764.  M13 is about 145 light years in diameter, and is composed of several hundred thousand stars.  With an apparent magnitude of 5.8, M13 is easily viewable in small telescopes or binoculars.

http://en.wikipedia.org/wiki/Messier_13

ABOUT THE IMAGE

DATE/TIME:  Evening of April 25th and morning of the 26th 2009

CAMERA:  Canon XSI, 450D

TELESCOPE:  Celestron 235mm SCT @ F/10

ISO SETTING:  400

EXPOSURES:  25

EXPOSURE LENGTH:  200sec

TOTAL EXPOSURE LENGTH:  50min

SUBTRACTIONS: 20 dark frames and 10 bias frames