Open Cluster  Collinder 399 - Coathanger   Vulpecula / Füchslein
Collinder 399 (Cr 399) is a random grouping of stars located in the constellation Vulpecula near the border with Sagitta. Collinder 399 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 number, 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 1980s, Pavlovskaya and Filipova were looking for common proper motion of open clusters, and found that the Coathanger was sharing spacial 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)
G53F + Pulsar2,  Tripod: GHS kII Qlock RA / DE
19 26  /  + 20 11
Telescope Takahashi FSQ 106ED Size
Camera Moravian G2 8300FW
Filter Astrodon LRGB 1,25''

Exposure L 63x3min R/G/B - 12/13/14  x 5min 

6h 24min
Software PixInsight, Photoshop

Inzersdorf / Oberösterreich
AAPOD2,  Sky & Telecope 11/2016