Collinder 399 – Al Sufi’s Cluster, Brocchi’s Cluster, The Coathanger

Bordering between the constellations, Vulpecula and Sagitta. This randomly formed cluster of stars forms the shape of a coathanger giving it it’s common name, The Coathanger. Discovered in 964 by a Persian astronomer by the name of Al Sufi, and mentioned in his book, Book of Fixed Stars. Later it was idependently rediscovered by an Italian astronomer named Hodierna in the 17th century. In 1920 an amateur astronomer named Brocchi created a map of the Coathanger and used it for calibrating his photometers. In 1931 a Swedish astronomer named Collinder added this to his catalog of open clusters.

Enlarge image, the coathanger can be seen near the middle of the screen shot.

Enlarge image, the coathanger can be seen near the middle of the screen shot.

These stars are were though to be an open cluster up until the late 20th century when it was determined that it is not an open cluster, but just a chance alignment of stars. 10 stars make up the Coathanger and they range from 5th to 7th magnitude with a straight line of 6 stars and 4 forming the hook. In dark enough skies this can be seen with the unaided eye or with a pair of binoculars. This large object is best seen with low magnification since the higher magnification used the more stars of the cluster are cut off from the asterism itself.

Coathanger without street light blocked

Coathanger without street light blocked

Coathanger with street light blocked

Coathanger with street light blocked







These images were taken from my front yard where I have a very bright street light. Two images above show a comparison of me blocking the light from the street light while imaging, and the other image shows an image without blocking the light. Neither image has been edited, only converted from a RAW file to a JPEG.

Collinder 399. 07-06-13

The above image is only 4 images with an exposure of 1 minute a piece, and ISO 800, I used 25 dark frames to remove as much noise as possible.

Screenshot of object location taken in Stellarium. Image stacking in Deep Sky Stacker.

Omni XLT 150 with CG-4 mount
Modded Canon 350D
T-ring and adapter
Polar Scope for alignment

August 4th, 2011 Viewing Session – M27 and Coathanger Asterism

I went onto my back porch to do my viewing last night (all my observations were made on the 5th of August) because the two objects I was after were clearly visible even with the tree cover I have in my yard. I was after M27 – The Dumbbell Nebula, and I was after the asterism known as Brocchi’s Cluster, or Coat-hanger Asterism.

M27 – Dumbbell Nebula is a Planetary Nebula (magnitude 8.10) in the constellation Vulpecula which is latin for “little fox”. Vulpecula is very close to the constellation Cygnus, and just below it is the constellation Sagitta which is latin for “arrow”. I spent quite a bit of time looking for the Dumbbell Nebula because for some reason I couldn’t pinpoint it even with the help of Stellarium, and The Pocket Sky Atlas from Sky & Telescope. Once I finally found it I attempted to take a few pictures, then it dawned on me; I should get into trying to sketch objects I see. I found sketching to be a great way to study the detail of an object, and to spend quite a bit of time with it. The more time you spend looking at something the more you start to see. Also after sketching I wrote a few notes to help remember what I saw. My eye was wandering all over the eyepiece looking at all the stars. Some stars were only visible with averted vision while other were quite bright and easily seen looking directly at them. I used both my 32mm eyepiece giving me a magnification of 31.25, and the 12.5mm eyepiece giving me a magnification of 80. In both magnifications the nebula is very faint and fuzzy, although it seemed to me just as bright, if not a tad bit brighter in the 12.5mm surprisingly. Usually the higher the magnification the dimmer an object gets. I could just barely make out a dumbbell shape in the nebula through both eyepieces, detail was a bit better in the 12.5mm. While sketching and viewing I saw what I’m going to call space junk flying through my view through the eyepiece. It could have been a satellite but it was very dim and couldn’t see it with the naked eye, and stellarium didn’t show any satellites in the area at the time (12:45am Aug. 5th). With both eyepieces I wasn’t able to make out any color, which is normal when viewing. Color usually starts to show with long exposure photography or very very dark viewing areas that lack light pollution. I also noticed and took note that with the 12.5mm eyepiece the nebula seemed to almost “pop out” and appeared closer than the background stars in the field of view.

Photograph is 6 pictures stacked. ISO400 F3.1 30sec exposures.

Next was Brocchi’s Cluster/Coat-hanger Asterism which is an average of around a magnitude 6. Also in the constellation Vulpecula, but very close to Sagitta. With the naked eye from my back porch it looked like a very small fain cloudy/fuzzy light. I almost couldn’t see it, again averted vision was key in spotting it. I only used my 32mm eyepiece which just fit the entire thing into my view. No sense in using a higher magnification if I’m just going to see less of the object I’m looking at. The more I’m into astronomy the more I realize how important a good low power eyepiece truly is. In the cluster I was able to make out around 27 stars clearly, although a couple were only visible with averted vision (if you haven’t noticed averted vision helps A LOT when viewing). Of the 27 stars that I saw there were around 10 of the brightest ones that made up the coat-hanger shape. There is no nebulosity to this asterism it’s just a nice little open cluster of stars that happen to look like a coat-hanger just floating overhead.

I ended the night watching the ISS pass at 2:40am and was tempted to bring the scope back outside to look for Andromeda again since it was high up in the sky, but I was too tired and decided it can wait until it rises earlier or until next time if I can stay up late enough to view it. Another great night in the Adirondacks with great viewing.