Chaple’s Arc
August 2009 :
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.
This summer you can view a famous Ring (M57) for the gazillionth time, or you can be one of the few to glimpse a much lesser-known Ring (the Fairy). Here’s how to find it. Using a low-power eyepiece, trace a line from eta Cygni to 25 Cygni and extend it a half degree beyond to the Arc.
For an interesting discussion on Chaple’s Arc/the Fairy ring, read the Cloudynights thread in the subject. Whether you call it Chaple’s Arc or the Fairy Ring, this is one asterism that will astound and delight you.
Your comments on this column are welcome. E-mail me at gchaple@hotmail.com.
