M2 - Globular Cluster, Aquarius
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Globular cluster M2 was discovered by Jean-Dominique Maraldi on September 11, 1746. Messier independently rediscovered and cataloged it exactly 14 years later, on September 11, 1760, as a "nebula without stars." William Herschel was the first to resolve it into stars.

M2 has a diameter of about 175 light-years, contains about 150,000 stars, and is one of the richer and more compact globular clusters. Visually it is of apparent magnitude 6.5 and about 6 to 8 minutes of arc in diameter, with a bright, compressed central region of about 5'. From its color-magnitude diagram the age of M2 as estimates at about 13 billion years and to be about the same as that of globular clusters M3 and M5. M2 is approaching us at the low velocity of 5.3 km/sec.

M2 is found rather easily from Alpha and Beta Aquarii, as well as Epsilon Pegasi. It is 5 degrees north of Beta Aquarii, on the same declination as Alpha Aquarii.

With its visual magnitude of 6.5 mag, M2 is a difficult object for naked-eye observing (just not visible under "average" conditions), but an easy target for the slightest optical aids like binoculars. In particular as it is situated in a star-poor field. With an 8-inch, this globular cluster is partly resolved into stars, well into the center under good viewing conditions. Larger scopes, 10-inch up, are required to fully resolve this cluster.

  Location J65 Celbridge Observatory
  Date/Time (UTC) 29 August 2006, 21:30
  Optics 200mm SCT, F6.3 reducer
  Filters None
  Imager Meade DSI-C
  Mount Astro-physics 1200GTO
  Exposure details 10 images * 60 seconds
  Software MaximDL, Photoshop 7
© David McDonald 2012 Updated 10 June 2012