Collinder 399

Collinder 399 (also known as Brocchi Cluster, Perch Cluster or Al Sufi Cluster) is an asterism located in the constellation of Vulpecula. It was first described by Persian astronomer Abd Al-Rahman Al Sufi in his Book of Fixed Stars in 964, and independently discovered again by Giovanni Battista Odierna in the seventeenth century. In the 1920s, amateur astronomer D. F. Brocchi created a map of this object for use in the calibration of photometers.

The asterism is composed of ten stars between fifth and seventh magnitude that visually present the appearance of a perch, a straight line of six stars "with a hook" four stars on the south side.

The status of this cluster as a star cluster has changed in recent years. The main stars were cataloged as a cluster opened by Per Collinder in 1931, and the group was considered as such for most of the 20th century. However, using a variety of criteria, in 1970 it was concluded that only six of the brightest stars actually formed a cluster; Moreover, several independent studies since 1998 have determined that the object is not a true cluster at all, but simply a random alignment of stars. In general, these studies base their conclusions on more precise measures of parallax and self-motion provided by the Hipparcos satellite first published in 1997.

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