2019 July 26 ~ Cr 399 (Brocchi's Cluster) in the constellation Vulpecula [WITH LABELS]

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Photographed at Algonquin Provincial Park, Ontario, Canada

(285 km by road north of Toronto)

between 23.42 and 23.52 EDT

* Altitude of the cluster at time of exposures: 64°

* Temperature 19° C.

 

* Total exposure time: 5 minutes

* 660 mm focal length telescope

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Description:

 

One of the easiest open clusters of stars to spot with the unaided eye - and a lovely object in binoculars or a very wide-field telescope - is Collinder 399, also known as "Brocchi's cluster" or the "Coat Hanger" because of its distinctive shape.

 

From Wikipedia:

 

"Brocchi's Cluster (also known as Collinder 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.

 

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.

 

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."

 

To the left of centre is the smaller, richer star cluster NGC 6802, and near the top edge, right of centre is the small hydrogen II gas cloud Sh2-83.

 

For a version of this photo WITHOUT LABELS, click on your screen to the LEFT of the photo, or click here:

www.flickr.com/photos/97587627@N06/48398730457

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Technical information:

 

Nikon D810a camera body on Tele Vue 127is (127 mm - 5" - diameter) apochromatic astrograph, mounted on Astrophysics 1100GTO equatorial mount

 

Five stacked subframes; each frame:

ISO 2500; 1 minute exposure at f/5.2, unguided

(with LENR - long exposure noise reduction)

 

Subframes stacked in RegiStar;

Processed in Photoshop CS6 (brightness, contrast, levels, colour balance)

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Done