Teutsch 22, Open Star Cluster
"Teutsch 22" is an open star cluster in the constellation of Swan, which according to the latest data of the GAIA mission is located at a
distance of 12,800 light years. Using the apparent visual diameter of 2.5' (arcminutes) one gets therefore a true size of 9 lightyears.
The brightest stars reach a magnitude of 13mag, while the majority is 15mag and below. So you need an aperture of 40cm to resolve
the cluster reasonably into single stars. Altogether about 90 stars are attributed to the cluster, which are clearly reddened with a value
of E(B-V)=0.71. The age of Teutsch 22 is given with 390 million years.
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In a 20 inch telescope a nice star cluster shows up, which is resolved into 15-20 single stars at a magnification of 270x. The shape of
"Teutsch 22" appears irregular and two star concentrations are visible. A diffuse or grainy background is only very subtly present. So
with a little more aperture more stars could be visible. Definitely one of the simpler star clusters of this catalog.
Also in the field of view are two bright stars that provide a nice contrast.
