17 November 2015
Open Clsuter Collinder 399 -
399 (Cr 399) is a random grouping of stars located in the
constellation Vulpecula near the border with Sagitta.
is known as Al Sufi's Cluster or Brocchi's Cluster. The
brighter members of this star cluster form an asterism
also known as the Coathanger.
This cluster of about 40 stars was discovered by Al Sufi
and described in 964 AD. It was independently rediscovered
by the italien astronomer G. B. Hodierna (17th century).
Messier, the Herschels and the NGC did not assign it a
probably because of the cluster's size: Even at
moderate power, it doesn't match in one field of view, and
is best seen in a good pair of binoculars.
Also, its appearance suggests it might be an
asterism only. This object is sometimes named Brocchi's
Cluster after American amateur astronomer D.F. Brocchi,
who created a map of it in the 1920s, for
calibrating photometers. It was included in Per
Collinder's 1931 catalog of open clusters.
In 1970, investigations of Hall and Landingham
revealed that perhaps only 6 of the brighter stars and
none of the fainter
ones appear to have a common proper motion, thus
indicating that they may form a cluster. In the late
and Filipova were looking for common proper motion
of open clusters, and found that the Coathanger was
motion with about 10 other clusters, including the
Plejades (M45), NGC 6633, 6709, 6882, 6885, and IC 4665.
Collinder 399 was found to approach us at 18 km/sec. (info
from Bernd Nies)
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