Chaple’s Arc and the Cygnus Fairy Ring

  • Date of observation:  August 13th 2015
  • Transparency:  Poor – Very high humidity  
  • Seeing:  Excellent
  • Telescope:  10-Inch f/4.5 Reflector

I located and recognized immediately using a 32mm eyepiece @ 36x with a 1.8º FOV.  The first star I noticed was double star h1470, with the primary being a ruddy or rust color.  

When increasing the magnification, using a 20 mm eyepiece @ 57x with a 1º FOV, at least eight or more pairs of double stars, making a circle could be seen and separated.  This beautiful ring of doubles are framed very nicely within the 1º field.  A fabulous and most interesting asterism. Dimensions: 40 x 40 arc minutes.    

A pencil sketch by the writer using a blank 5 x 8 notecard with the colors inverted using a scanner.

Scanned Image 160890002

Now for the complete story of Chaple’s Arc, and how the Cygnus Fairy Ring came to being…

The following is an excerpt from an article by Glenn Chaple and posted by “Skyscrapers, Inc.” 

“Forgive me for the apparent ego trip, but this month I’m going to introduce you to an amazing little asterism called “Chaple’s Arc.” I stumbled upon the Arc in the mid-1970s while looking for the double star h1470. Instead of one double, I found four arranged in an arc 1/2° across. So smitten was I by its extraordinary appearance that I eventually wrote about it in the September 1980 issue of Deep Sky Monthly. New York amateur astronomer John Pazmino viewed the group and dubbed it “Chaple’s Arc.”

A quarter century later, I decided to introduce the Arc to a much larger audience by featuring it in my “Observing Basics” column in Astronomy. To my amazement, I saw the same group described in the British magazine Sky at Night. The writer called it the “Fairy Ring.” Uh-oh! Had I missed something?

After a little detective work and an assist from Sky and Telescope’s Sue French, I learned that the Arc had been seen by Utah amateur astronomer Kim Hyatt in the early 1990s. Like me, he found it during a search for h1470. Because he was using a larger telescope than I had, he was able to view some faint pairs that, along with my four, formed a ring of double stars. Not knowing about Chaple’s Arc, he and a friend christened it the Fairy Ring.”   Glenn Chaple/Skyscrapers, Inc. 

Chaple’s Arc:  Image by Mario Motta:  August 29th 2022  

I attached two images, first a wide field centered on the arc or fairy ring. Note in the wide-field that it has a surprise “dark dust lane” immediately above and below the circle of double stars, and in the south edge of the field is a faint nebula glowing.
This was taken with my 6-inch f/7.6 refractor, that gives a 1.0 x 1.4 degree field of view with my ZWO ASI6200 camera. 
One can see the ring of double stars, but also many other double stars in this interesting field.
This was 10 stacked 10 second images, lightly processed only, to hone in to the Chaple Arc.  I also cropped the image to highlight the arc (ring) itself. 
Glenn, I am including you in this email, in case you don’t have an image of your immortality in the sky… 🙂   Mario Motta 

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