I hope you were able to catch a moonrise the past two nights. We were cloudy here though the clouds parted late and let a few moonbeams pass. Now that the moon is waning and rising later it won’t be long before dark skies return. While you’re waiting, allow me to share three of my favorite binocular asterisms.
We’ve touched on asterisms before — bright, conspicuous stars within a constellation or shared by one or more constellations that form a distinctive pattern. The Big Dipper may be the most familiar asterism followed closely by the Belt of Orion. Neither is a constellation, but both are bright, easy-to-spot arrangements of stars. This time of year, the most prominent asterism is the Summer Triangle, formed by the three bright stars Vega, Deneb and Altair. Together they connect into a huge triangle that measures four outstretched fists tall and two wide. As soon as it gets dark, look high up in the south-southeastern sky and you can’t miss this monster geometrical figure.
Beside these striking, naked-eye patterns there are also dozens of binocular asterisms. One of the brightest and most whimsical is called the Coat Hanger located just below the Northern Cross (itself an asterism!) in the faint constellation of Vulpecula the fox. Northern Hemisphere observers see the hanger upside down, but either way it really looks like its name. For some time it was considered a true star cluster and still bears the name Brocchi’s Cluster, but the figure is only a happenstance alignment of unrelated stars.
From a dark sky site, the Coat Hanger is faintly visible without optical aid and looks like a small, glittery patch, but binoculars really breathe life into the little group and clearly reveal its wiry shape. I see it super well in my 10x50s, but any pair will do. Four stars comprise the hook, while six or more make up the supporting bar. The effect is quite striking, and once you happen upon it, you’ll wonder how it eluded you so long.
Two more binoculars asterisms — the Airplane and Lucky 7 — are well-placed during the early evening hours just above the W of Cassiopeia. To find Cassiopeia, look halfway up in the northeastern sky around 9 o’clock local time. The Airplane is made up of about 15 stars bright and faint spread across 1° of sky. Five stars, including the four brightest, shape the front of the plane and wings, with nine fainter stars to the left that define the fuselage and tail. Patterns are fluid and depend on who’s looking — some see a dragonfly here instead. Lucky 7 is twice as large and looks just like its name except it’s upside down this time of year. As with the Coat Hanger these are all random associations of stars that our eyes sense as patterns.
Although all three groups are visible in moonlight, they’ll look more striking when the bright moon is out of the way. There are lots of great binocular asterisms, and I’ll be featuring more in the weeks ahead. I’m even wagering you’ll make up a few of your own as you seek these out. Seeing and making patterns is not only fun but also instructive as little by little we become more familiar with the night sky.