M69 is a globular cluster located inside the prominent teapot asterism of Sagittarius. It shines at magnitude +7.6 and is therefore within the range of good quality 7x50 or 10x50 binoculars, although it appears faint and star like.
This globular 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, which is a physically close neighbour of M69. Spatially, they are separated by just 1,800 light-years and any potential observers located on planets inside one of these clusters, would have a spectacular view of the other and vice-versa. Of course, this is assuming that the many thousands of bright stars, visible in their own backyard, didn't block the view of the other cluster.
Finding M69 is easy once one is familiar with Sagittarius. Start by focusing on the base of the teapot and then image a line connecting Kaus Australis (ε Sgr - mag. +1.8) with Ascella (ζ Sgr - mag. +2.6). M69 is positioned 1.5 degrees along and 2 degrees to the north of this line. There are two 5th magnitude stars located just south of the cluster.
M69 is best seen from the Southern Hemisphere during the months of June, July and August. From mid-northern latitudes, it's a difficult object that never climbs particularly high above the southern horizon.
When viewed through 80mm (3.1-inch) refractors, M69 appears small with a bright centre surrounded by a faint halo. It looks somewhat like a comet but even at high powers isn't resolvable. Of the three Messier globulars (M54, M69 and M70) inside the teapot, M69 is the brightest. All three clusters are fine examples in their own right, but they suffer from small apparent sizes and are difficult to resolve with amateur scopes. Nevertheless, a 200mm (8-inch) reflector at high powers reveals M69 as a sharp centre that tails off gradually in brightness towards the outer edges. Averted vision helps, but to get the most out of this globular a larger scope is recommended.
In total, M69 has an apparent size of almost 10 arc minutes but visually 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 couldn't find any variables and to date only 8 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|
|Age (years)||13.06 Billion|
|Number of Stars||125,000|
|Notable Feature||One of the most metal rich globulars known.|