President's Corner

When Telescopic Asterisms… Aren’t 
by Charles Ennis, Sunshine Coast Centre 
I first viewed Brocchi’s cluster, popularly known in Western culture as “the Coathanger” at the telescope eyepiece of fellow astronomer Danny Sklazeski, and it has been a go-to for me at outreach ever since. The Coathanger appears on every list of telescopic asterisms I’ve ever seen. I first viewed the open cluster Messier 44 (the Beehive Cluster) and the double-star system Mizar and Alcor at the eyepiece of my own telescope. It wasn’t until I got involved in RASC’s World Asterisms Project that I discovered that these three asterisms are not telescopic asterisms at all. 
Brocchi’s Cluster is listed in many texts as having been discovered by Italian astronomer Giovanni Battista Hodierna in 1654, and it is named for American amateur astronomer Dalmero Francis Brocchi, who created a map of it in the 1920s. However, the first recorded unaided eye sighting was by famous Persian astronomer ’Abd al-Rahman al-Sufi in 964. The Beehive was observed by Galileo in 1609, and was added to French astronomer Charles Messier’s catalogue in 1769. However, this open cluster appears as “the Crab” in ancient Babylonian cuneiform texts. Hipparchus called it “Little Cloud,” Aratus called it “Little Mist,” and Eratos­thenes and Ptolemy called it “the Manger.” Chinese astrono­mers of the Ming Dynasty called it “Cumulative Corpse Gas” and ancient Korean astronomers called it “Pile of Dead.” Ancient Babylonian texts refer to Alcor as “the Fox.” Ancient Mongolians called Alcor the “Recover and Protector Star” and believed Alcor had been placed there by their God of Heaven, Tengeriin, to protect Mizar. They believed that you could not be an archer unless you could see both stars. In the Ming Dynasty, astronomers called Alcor “the Assistant.” Clearly people all over the world could see these asterisms with the unaided eye before the invention of the telescope. Why are they now typically listed as “telescopic asterisms”? 
The misuse of artificial light at night is what happened. Billions of dollars are wasted every year on excessive and improper lighting, disrupting the migratory patterns of birds, disrupting peoples’ circadian rhythms, and decreasing safety by blinding people at night with the glare. That is why I’m pleased to see that the RASC’s Light-Pollution Abatement Committee is now beginning work with two Canadian communities, one from each end of the country, to help them become Dark-Sky Communities. This involves working with them to amend By-Laws to require full-cutoff lighting of the correct colour temperature. New construction will require this lighting, and in the coming years, as old systems need replace­ment, they will be converted to the new standard. This is definitely possible: One of those communities is Sechelt, B.C., which is where I live. Twelve years ago, our astronomers in the Sunshine Coast Centre took sky quality measurements all over the coast. I repeated these measurements in 2019 to determine how much the sky quality had degraded due to ongoing construction and expansion. Sechelt had been putting up new full-cutoff street lighting since the original tests. I was pleased to see that the readings a decade later had not increased. As a result, these communities will save money, improve safety, improve health, and restore these asterisms to the list of unaided eye asterisms where they belong. 

Last modified: 
Friday, September 16, 2022 - 12:10am