M13 is likely the most famous globular cluster in the northern hemisphere. A combination of its large true size of just under 150 light-years, nearly half again the size of a typical globular cluster and its rather close distance of 25,000 light-years make it the largest globular in the northern sky. The southern sky has two even larger, so large they were both originally cataloged as stars.

M13 was discovered by Edmond Halley in 1714. Charles Messier recorded it on June 1, 1764. Its age is often stated as older than the universe which is impossible of course. Safe to say it is very old and may predate our galaxy's formation. That would mean it was captured from another galaxy ours likely disrupted in its early days.

You can read more on this at: http://messier.seds.org/m/m013.html

As with most M objects, I took this one back in 2007 when I didn't quite understand what I was doing and my processing skills were rather poor. Since this one turned out fairly well I've not reprocessed it though it could use this treatment.

14" LX200R @ f/10, L=6x5' RGB=2x10', STL-11000XM, Paramount ME