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| M22, A globular cluster (NGC 6656) |
| M22 is a very remarkable object. It can easily be found with binoculars just to the left of the Teapot's topmost lid star. It is visible to the naked eye for observers at not too northern latitudes. The Hercules cluster (M13) is often considered one of the finest northern globular clusters, but in my opinion, this great cluster is its equal, if not the better. In fact it is both brighter and bigger, but it is relatively low in the sky at 23 degrees below the celestial equator. It resides on the eastern side of the milky way, and in the near company of many of the clusters and nebulae from that part of the sky. For the observer, it is of interest that M22 is less than 1 degree of the ecliptic, so that conjunctions with planets can occasionally be observed. At 10,400 light years, it is one of the nearer globular clusters. At this distance, its 32' angular diameter, slightly larger than that of the Full Moon, corresponds to a linear width of about 97 light years; visually, it is still about 17'. At least 100,000 stars have been counted in a roughly 200 light year central diameter. Recent Hubble Space Telescope investigations of M22 have led to the discovery of a considerable number of planet-sized objects which appear to float through this globular cluster; these objects may have masses of only 80 times that of Earth, and were discovered by so-called micro lensing effects, i.e. bending of light of background member stars of the cluster. |
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10"
F6.3 Schmidt Cassegrain Telescope, (1600mm F.L.) Modified Canon
300D camera with Baader IR-UV filter and coma corrector, placed at the scopes prime focus |