I'll Say it again; this is a great target to observe using binoculars ...
Monday June 23rd was forecast to be a clear night (the second clear night in a row). I was able to get my astrophotography rig set up before dark. Since we were so close to New Moon, I looked for a broadband target that would get high above the trees that obscure my horizon and would be appropriate for my wide field set up. Collinder 399, The Coathanger Asterism fits the criteria. The only thing that gave me pause is that I imaged this target previously, at a longer focal length (click here to view the blog post). After looking at this target in the Framing Wizard in NINA, I decided to go for it.
Targets like this one are not as "exciting" as
emission nebula or galaxies, but I'm always overwhelmed by the enormous number
of stars contained within the field. Furthermore, The Coathanger is a great
target to observe using binoculars. Regardless of whether you are an
experienced amateur astronomer with many telescopes or you are just getting
started with astronomy, binoculars are super useful for observing. Most people
have access to binoculars, and they are a great way to get started in the
hobby. I have a pair at home and a pair I keep in my truck. This target is very
easy to find (see the "How to Find" section below). I never get tired
of looking at it.
The evening went relatively well. I got everything set up and connected. After polar aligning the mount and calibrating PHD2, I began the imaging sequence. The first sub came in at 10:42 PM. I went to sleep, soon after that. The rig continued to collect subs until 3:58 in the morning. Here's the resulting image.
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| An image of Cr 399 - The Coathanger, captured from my backyard on 06/23/2025 |
Processing:
All pre and post processing was performed in PixInsight. Pre-Processing: All subs were visually inspected with Blink and subs with issues were removed. All light Frames, Flats, Darks and Dark flats were loaded into WBPP. Linear Post Processing: Background extraction was performed with GraXpert followed by BXT (correct only). SPCC was used for Color Calibration followed by a full application of BXT. The Stars were removed using StarXT. Starless Linear: Noise was reduced with NXT. The image was made non-linear with HT. Linear Stars: The stars were made non-linear with Seti Astro's Star Stretch Script.
Non-linear Post Processing: Starless: Color, intensity, and contrast were adjusted with various applications of CT. Saturation was increased with CT. The DSE script was used to enhance dark nebula regions. Stars: Saturation was increased with CT. Final: The Stars and Starless images were combined with Pixel Math to produce the final image. CT was used to adjust contrast one last time.
What is it?
The Coathanger is known as Collinder 399 (Cr 399) or Brocchi's Cluster. This object is an Asterism (a prominent or recognizable pattern of stars). It is not a true open star cluster, it is a chance alignment of 10 bright stars. There are about 30 more stars that some consider to be a part of the asterism.
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| An annotated image of Cr 399. |
How big is it?
This object has an angular distance of 89 arcminutes (1 degree is 60 arcminutes) on the night sky.
How far is it?
It is located about 4,200 light-years (ly) from Earth in the Constellation Vulpecula.
How to find it?
This is object is relatively easy to find in a pair of binoculars, optical finder scope, or telescope with a wide field of view. It is located in the Constellation Vulpecula which is a dim constellation located within the Summer Triangle. Use the finder chart below to help you locate it.
- Find the Summer Triangle (Vega, Deneb, & Altair).
- Method 1:
- Find Albireo (a beautiful visual target itself) which is the head of Cygnus the Swan or the base of the Northern Cross.
- Find the star Alpha Vulpecula and draw an imaginary line from Albireo through Alpha Vulpecula. The Coathanger is roughly the same distance from Alpha Vulpecula as Alpha Vulpecula is from Albireo.
- Method 2:
- Find Vega and Altair and draw an imaginary line between them.
- The Coathanger is roughly between both stars (it's a little closer to Altair).
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| Finding Chart for Cr 399 |
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