Teutsch 27, Open Star Cluster
The open star cluster "Teutsch 27" is located at a distance of 9,600 light-years in the constellation Arrow. With an apparent diameter of 0.8' (arcminutes) the
cluster is very small and appears in the telescope just as large as the planet Jupiter. From the apparent size the true diameter can be determined to 2.3 light
years. For a star cluster a very small value.
Only 20 stars are attributed to the cluster, so it can be described as star-poor. The stars are also strongly reddened because they are shielded by upstream dust.
So the brightest stars in "Teutsch 27" reach only a magnitude of 14.5mag. Only 8 stars are brighter than 16mag.
The age is given with 87 million years, so it is a rather young representative of its kind.
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In my 20 inch f/3.2 Dobson telescope the cluster appears as a diffuse glowing spot at a magnification of 120x. No single stars are visible. But at 270x about
7-10 single stars peel out of the diffuse background, moreover the cluster seems to have a triangular shape. Compared to other star clusters "Teutsch 22"
seems to be very small. The surrounding area is star-rich, which makes the sight very attractive.
