Discovered by Charles Messier in 1764.
M12 [also designated NGC 6218] was once believed to be an intermediate type between a globular and a dense open cluster. Although it is not as concentrated as most other globular clusters we are usually familiar with, it is now generally classified as a true globular. It lies in the direction of the constellation of Ophiuchus at an estimated distance of 17,500 light-years. The apparent diameter of M12 corresponds to about 75 light-years. The rich star colors in and around this cluster make for a very pleasing image.