NGC 6517, Globular Cluster
The globular cluster NGC 6517 is located at a distance of 38,000 light-years in the constellation Serpent (Ser) and was discovered back in
June 1784 by F.W. Herschel.
The brightness of the cluster is 10.1mag, its apparent size only about 4.0 arcminutes. It belongs to class IV, which is why the center is quite
dense. The mass of NGC 6517 is given as 526,000 solar masses, the absolute magnitude as M= -8.25mag, which corresponds to a luminosity
of 210,000 suns. From the apparent diameter, the true size can be determined to be 44 light-years, which is a very small value for a globular
cluster.
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In my 20" telescope, NGC 6517 still appears very small even at a magnification of 270x, but compact and bright. It shows a bright, strongly
concentrated core. Even at this magnification, there is no chance of resolving the globular cluster, not even in the outer regions - no individual
stars are recognizable. The background does not even appear grainy, but completely diffuse. :(
