Welcome back, sky walkers. I hope you found the time to watch the recent lunar eclipse. Perhaps you joined the large gathering of local sky walkers that assembled on the Slough Road conservation land to observe it among friends and neighbors.
The northern sky. (Drawings by Marc Vilain) CLICK IMAGE TO ENLARGE
For the next few columns, we will be looking northward. The large chart at right shows the northern sky as it appears this month in the early evening. On the left is the familiar bowl of the Big Dipper, drawn here with additional stars and lines to form the shape of the Great Bear (Ursa Major). Polaris, the North Star, is in the upper center of the picture; it is the outermost star in the handle of the Little Dipper (Ursa Minor).
We will have more to say about the bears in an upcoming column. Today, however, we will be turning our gaze to two other constellations: Cassiopeia and Perseus. Cassiopeia, the queen of Greek mythology, is diametrically across Polaris from the Big Dipper. The ancient Greeks pictured her sitting in a throne, but to my eye, she looks like a slouched version of the letter W after it had a bad day at the office. Below Cassiopeia is the Greek hero Perseus; he’s a stick figure in the chart, but in the sky he looks much more like a tilted kitchen funnel.
At this time of year, Perseus and Cassiopeia are perched in the evening sky some 30 to 45 degrees above the horizon, having cleared treetops and the worst of the artificial sky glow. This makes them an ideal destination for binocular observation. What you will need is a good pair of binoculars, the kind you might already own for birding or nature watching. Mine are a moderately priced 10×50 pair, for example.
Perseus perspectives
We will start our celestial ramble with Perseus, pictured in greater detail in the star chart at left. The brightest star in the constellation is Mirfak, a name that comes to us from the Arab astronomers of the Middle Ages. This nomenclature is not a coincidence; the stars of the sky are a treasure-trove of Arabic names, a testament to the foundational work of scientists of the Islamic Golden Age.
You will know immediately that you have sighted Mirfak in your binoculars, as it is surrounded by a veritable riot of bright stars. These stars are an afterthought to the naked eye, but they will really jump out at you with binoculars. To astronomers, they are the α Persei association, α Persei being the technical name for Mirfak. If you dwell on these stars for a moment, you might see shapes suggesting themselves to your mind’s eye. I see a curvy mountain road, or perhaps a Chinese dragon.
Where to find the Double Cluster.
CLICK IMAGE TO ENLARGE
Looking up from Mirfak, the region between Perseus and Cassiopeia is home to one of the greatest binocular sights: the Double Cluster. Start from the pointed end of the Perseus funnel (the head in the stick figure), and sweep your binoculars up and slightly to the left; the trajectory that you’re following should lead you to the bottommost branch of Cassiopeia’s slouching W. About half to two-thirds of the way up is the Double Cluster. To my eyes, this appears in binoculars like an oval necklace of stars. Hanging off the bottom of the necklace is a fuzzy-looking jewel with a larger one below that, the Double Cluster proper. The clusters may appear first as fuzzy-edged smudges, but steady hands or tripod-mounted binoculars allow the eye to discern dozens of the individual stars that make up the clusters. You will see even more detail with a telescope, such as the library’s StarBlast lend-a-scope.
If you can’t find the Double Cluster by sweeping up from Perseus, try sweeping down from Cassiopeia. The bottom branch of the W should stretch end-to-end across the binocular field of view; the Double Cluster is about one field of view’s distance down from there and slightly to the right.
Congratulations! You’ve just spotted your first deep-space object.
And with this, fellow sky walkers, we bring the guided portion of this walk to an end. I encourage you, however, to linger on with your binoculars in this corner of the sky. You are gazing right into a region of the Milky Way that is flowing with stars and rich with star clusters. There are several more clusters just one or two fields of view to the left (west) of the Double Cluster. Can you find them on your own?
Marc Vilain lives in the center of town. As an amateur stargazer, he has been walking the night sky for more than 20 years.
