Monday, October 14, 2019

The Stars of Cr 399 (aka Brocchi's Cluster)

Cr 399 aka Brocchi's Cluster (an "open" visual cluster)

As per my previous post, I thought I would have a little artistic fun by putting what I call my "StarCross" screen over the objective lens of a refractor. Since I was imaging under a FULL Moon it was difficult to capture the many stars and dark patches of the Milky Way in which this loose cluster of stars are located. I hope to try this again when the Moon is not hindering.

No, stars do not have "crosses". These are only caused by a screen or vanes located somewhere in the optical train of a telescope. My screen is just a piece of scrap chicken wire that has square openings about 1/2 inch in size (not the hexagonal or octagonal type.)

A little history and info on Cr 399:

Brocchi's Cluster (also known as Collinder 399, Cr 399 or Al Sufi's Cluster) is a random grouping of stars located in the constellation Vulpecula near the border with Sagitta. The members of the star cluster form an asterism which has given rise to its name as the Coathanger.

Ok, I will invert the image above and you will see why it has the name "Coathanger"...

History:
It was first described by the Persian astronomer Al Sufi in his Book of Fixed Stars in 964. In the 17th century, it was independently rediscovered by the Italian astronomer G. B. Hodierna. In the 1920s, Dalmero Francis Brocchi, an amateur astronomer and chart maker for the American Association of Variable Star Observers (AAVSO), created a map of this object for use in calibrating photometers. In 1931, Swedish astronomer Per Collinder listed it in his catalogue of open clusters.

Star Chart Location (in the lower right hand corner - in yellow:


The Facts:
The status of this group as a star cluster has changed in recent years. The group was considered to be a cluster for most of the 20th century. Looking at a variety of criteria, however, a study in 1970 concluded that only 6 of the brightest stars formed an actual cluster. Several independent studies since 1998 have now determined that this object is not a true cluster at all, but rather just a chance alignment of stars. These recent studies have generally based their findings on improved measurements of parallax and proper motion provided by the Hipparcos satellite which were first published in 1997.

Observing it:
The asterism is made up of 10 stars ranging from 5th to 7th magnitude which form the conspicuous "coathanger", a straight line of 6 stars with a "hook" of 4 stars on the south side. An additional 30 or so fainter stars are sometimes considered to be associated as well.
Under a dark sky, the Coathanger can be seen with the naked eye as an unresolved patch of light; binoculars or a telescope at very low power are usually needed in order to view the "coathanger" asterism. It is best found by slowly sweeping across the Milky Way along an imaginary line from the bright star Altair toward the even brighter star Vega. About one third of the way toward Vega, the Coathanger should be spotted easily against a darker region of the Milky Way. 

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