M69 is a globular cluster located inside the bright "Teapot" asterism of Sagittarius. It shines at magnitude +7.6 and therefore within the range of good quality 7x50 or 10x50 binoculars, although faint and only star like in appearance. The cluster is best seen from the Southern Hemisphere during the months of June, July and August. However, from northern temperate latitudes it's a difficult object as it never climbs high above the southern horizon.
M69 is located 29,700 light-years from Earth and was discovered by Charles Messier on August 31, 1780. On this night he also discovered M70, a physically close neighbour of M69; spatially they are separated by just 1,800 light years. Any potential observers located on planets orbiting stars inside M69 would have a spectacular view of M70 and vice-versa. Of course, this is assuming that the many thousands of bright stars visible in their own globular won't block the view of the other.
Finding M69 is easy once one is familiar within the teapot asterism of Sagittarius. Start by focusing on the base of the teapot and image a line connecting Kaus Australis (ε Sgr - mag. +1.8) with Ascella (ζ Sgr - mag. +2.6). Positioned 1.5 degrees along this line and 2 degrees north is M69, with two 5th magnitude stars located just south of the cluster.
When viewed through a small 80mm (3.1-inch) scope, M69 appears small with a faint halo surrounding a bright centre. It looks somewhat like a comet but even at high powers is not resolvable. Of the three Messier globulars (M54, M69 and M70) inside the "Teapot", M69 is the brightest. All three are fine clusters in their own right but they are small in apparent size and therefore difficult to resolve with amateur scopes.
A 200mm (8-inch) scope at high powers hints at resolving M69. Averted vision also helps but even larger scopes are recommended. The central cluster concentration is also apparent with a gradually tailing of brightness to the outer edges. In total, M69 has an apparent size of almost 10 arc minutes but through amateur scopes it appears much smaller. It's estimated to contain 125,000 stars and is extremely poor in variable stars. Outstanding twentieth century American astronomer Harlow Shapley could not find any and to date only 8 variables have been discovered.
M69 Data Table
|Object Type||Globular cluster|
|RA (J2000)||18h 31m 23s|
|DEC (J2000)||-32d 20m 53s|
|Apparent Size (arc mins)||9.8 x 9.8|
|Number of Stars||125,000|
|Notable Feature||One of the most metal rich globulars known.|