M12 is yet another globular star cluster in Ophiuchus. This constellation hosts more globular clusters than any other. It is some 15 to 16 thousand light-years from us. Rather close as globular clusters go. Assuming this distance and a size of about 16 arc minutes it is some 75 light-years across. Though I measure its size at 12 arc minutes on my image making it only 56 light-years across. But then my exposure time was very short, only 10 minutes rather than my usual 40 meaning I lost a lot of the outlying stars. Why I used such little exposure time I don't know recall and I left no notes.

The cluster was one actually discovered by Messier himself on May 30, 1764. For more on it see: http://messier.seds.org/m/m012.html

14" LX200R @ f/10, L=5x2' RGB=3x2', STL-11000XM, Paramount ME