NGC 366, Open Star Cluster
In the constellation "Cassiopeia" there are a lot of open star clusters - enough to spend many nights in this region of the sky. NGC 366 is one of the clusters
and is located in the middle of the celestial W, only about 2° away from the star "Gamma Cas". The cluster was found by John Herschel in 1829.
The cluster lies at a distance of 5,800 light-years. With an apparent dimension of 3' (arcminutes) the true diameter is calculated to about 5 lightyears. Color
images of NGC 366 show a distinct reddening of the stars - a consequence of the dusty environment in which the cluster is located. This is also evident from
the star-poor surrounding area. The brightest stars have an apparent brightness of about 12mag. This corresponds to an absolute magnitude of 0.7mag and a
luminosity of 45 solar luminosities. Here the weakening of the brightness by the dust in front of the star was not taken into account, so the true values are
probably higher.
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In a 20" telescope the cluster is a nice object despite the rather low number of stars. Even at 120x some brighter stars are noticeable. Also the background is
glittering a bit.
The cluster appears most beautiful at a magnification of 270x. The sky becomes pitch black and about 30 single stars with large brightness differences are visible.
The brightest stars are in the southeastern part of the cluster. The brightest of them is a double star which is easy to separate. The shape of the cluster is quite
irregular, but overall roundish. Two concentrations of stars are found in the south and east, while in the northwest a chain of faint stars is visible, separated from
the rest of the cluster by a starless strip.
