M2, also designated NGC 7089, is a globular cluster located in the constellation Aquarius.  It was discovered by Jean-Dominique Maraldi in 1746 and is one of the largest known globular clusters.  Charles Messier rediscovered it in 1760, but thought it was a nebula without any stars associated with it.  William Herschel was the first to resolve individual stars in the cluster in 1794.  M2 lies about 37,500 light-years from Earth and is approximately 13 billion years old.  It contains about 150,000 stars and at 175 light-years in diameter M2 is one of the larger globular clusters known.

http://en.wikipedia.org/wiki/Messier_2

ABOUT THE IMAGES

DATE/TIME:  1st image the evening of July 20th 2009.  2nd image, August 9th 2012.

CAMERA:  Canon XSI, 450Da

TELESCOPE:  1st image, Orion 100mm ED refractor @ F/18.  2nd image, Celestron C9.25 SCT @ F/6.3.

MOUNT:  1st image, Celestron CG5-ASGT.  2nd image, Celestron CGE Pro.

ISO SETTING:  800

EXPOSURES:  1st image, 60.  2nd image, 13.

EXPOSURE LENGTH:  1st image, 60sec.  2nd image 100sec.

TOTAL EXPOSURE LENGTH:  1st image, 1hr.  2nd image, 21min. 40sec.

SUBTRACTIONS:  20 darkframes, 10 bias frames

CAPTURE SOFTWARE:  MaximDL

STACKING SOFTWARE:  Deep Sky Stacker

PROCESSING:  Photoshop CS3