Messier 4 is the nearest globular cluster, being 2.2kpc or about 7,175 light years away. It is very prominent with the slightest optical aid, and is located just 1.3 degrees west of Antares in Scorpius.
Messier 4 would be one of the most splendid globulars in the sky if it were not obscured by heavy clouds of dark interstellar matter. Interstellar absorption also reddens the color of the light from the cluster. However it displays an angular diameter of more than that of the Full Moon, which corresponds to a actual diameter of 75 light years.
It is also one of the least concentrated globular clusters. The central core is much less dense than in many other globulars, such as 47 Tucanae.
OPTICS: 10" Serrurier truss Newtonian f/5
MOUNT: Losmandy G-11
CAMERA: QSI 683wsg
EXPOSURE: LRGB 45:21:21:21