A few nights ago I went out with my 10×50 binoculars for a quick session (tired, and with work in the morning, I couldn’t stay out late). Despite the brevity of the session, though, I was amazed at how much there was to see: open and globular clusters M11, M13 and M22; galaxies M81, M82 and M31; the Sagittarius Star Cloud; Eagle, Trifid and Omega nebulæ; the Veil supernova remnant; and amazing dark nebulae in and around the star Deneb, in the constellation of Cygnus. It really was an amazing session.
As impressive as these things were, it was a couple of other objects that impressed me the most: the Coathanger and Kemble’s Cascade asterisms. These are fantastic objects to observe in binoculars, and got me thinking about asterisms in general: what exactly are they; and how do they differ from star clusters and constellations.
Basically, asterisms are patterns of stars within constellations, and, because the component stars aren’t necessarily close to one another, they’re not true clusters.
Examples of large asterisms include the seven stars of the Big Dipper, making up, as they do, just a part of the Ursa Major constellation. Likewise, the five stars of the ‘W’ of Cassiopeia; the four of the ‘keystone’ in Hercules; the five of the ‘northern cross’ of Cygnus; the four of the ‘great square’ of Pegasus, etc.
However, it’s another ‘class’ of asterisms that I’m more interested in; what I’ll call ‘binocular asterisms’.
Kemble’s Cascade is a line of more than 20 colourful stars in the constellation of Camelopardalis, spanning approximately five moon diameters, and terminating in the open cluster NGC 1502, a small open star cluster of around 45 stars. Kemble’s Cascade is an ideal target for binocular viewing, as it just won’t fit in the field of view at higher magnifications.
The Coathanger asterism (also known as Brocchi’s Cluster), is comprised of 10 stars in the constellation of Vulpecula (the little fox). This really is a fun object, and really does look like a coathanger in dot-to-dot form. Like Kemble’s Cascade, it’s best viewed at low magnification, making it, too, an ideal binocular object.
There are many more asterisms up there, with such names as ‘Kemble 2’, the diamond ring’, ‘the 7 sisters of the pole’, ‘Medusa’s head’, and ‘Kemble’s Kite’. A more detailed list can be found here: https://www.saguaroastro.org/content/downloads.htm. And there are some lovely pictures here: https://www.deep-sky.co.uk/asterisms.htm.
I’m definitely going to make a point of seeking out more binocular asterisms over the coming weeks and months.
What’s up?
Once again the Moon is dominating things, and will continue to do so until after it’s full on the 16th. Even though the Moon will take deep space objects off the menu for a while, there’s still lots to see. The asterisms I mentioned above are all well placed.
The open cluster of the Hyades in Taurus is also ideally placed at the moment, can be seen even when the moon is bright, and makes for an impressive sight in binoculars.
The Orionid meteor shower peaks around the 21st of October, and should be on view in the East from about 11pm. Expect around 20 per hour at peak time.
Clear skies!
Kevin Quinn is an amateur astronomer based in Cerne Abbas. He is the proud owner of a ten-inch reflector, a small refractor, a case of eyepieces, and a couple of pairs of binoculars. He tweets via @CerneAstro, and blogs (occasionally) via theastroguy.wordpress.com.
©Kevin Quinn
