NGC 7686: A Trapezoid-Looking Cluster in Andromeda

NGC 7686 is an open star cluster in the constellation of Andromeda. It is best viewed during the autumn months.

With around 80 stars, it’s a 5th magnitude open cluster and is 23 light years in diameter. William Herschel discovered it on December 3, 1787.

My Observations

The brightest stars in the cluster make close to a trapezoidal shape. I’ll call it my “trap” cluster. The top right star in my eyepiece separates itself from the others by its buttery yellow. I can’t put my finger on why, but I’ve enjoyed studying this cluster on this December night. Looking up the history on NGC 7686, I’ve come to realize William Herschel discovered it on December 3, 1787 — 233 years from tonight as I view it.

Also observed on November 18, 2022, at 9:14 p.m.: This sketch at fifteen after nine is the last one of the night. The hoar frost crunches at my feet, and my fingers are so cold from sketching at the scope for two hours. The temperature is now 32 F, but my heart is grateful, for it has been five days of clear, cold, crisp skies every night. The Seattle rains will return this weekend, but before they do, I’ll take this moment to enjoy the buttery yellow star burning warm like a spark on this freezing night.

Key Stats

Constellation	Andromeda
Best Viewing	Autumn
Visual Magnitude	+5.6
Absolute Magnitude	-5.3
Distance from Earth	5,000 ly
Diameter	23 ly
Apparent Size	16 arcmin
Milky Way Location	Orion Arm
My Viewing Grade	B

Sources and Notes

Photo of NGC 7686 by Roberto Mura pulled from Stellarium. This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Sketch by Wayne McGraw