This month we have a guest review by our member Alister Ling. Read on!
When I was a teenager I had been content coming across the occasional jewel of a rainbow or 22-degree halo, but suddenly a window into the treasure room of the skies swept open before me. Four years into my RASC membership, this book was reviewed in Sky & Telescope, and my jaw dropped like someone seeing the Moon through a scope for the first time.
But an older book in today’s click-click world? Sure you can find out a fair bit on the internet, specifically at Les Cowley’s Atmospheric Optics website, but you miss out on the author’s story-telling of his journey of personal discovery, one that will soon be yours too. He maps out in detail how most halos change shape as the Sun (or Moon!) rises (sets) in the sky. All this with clear diagrams and no equations. Also, when you’re on the internet, it really helps to know what you’re looking for! If you are like I was at the beginning, you will appreciate a guide to show you what is even possible.
Thanks to Greenler’s explanations, I have seen segments of halos behind me, from a plane, on the grass at the golf course, in the fog, under a pollen-filled flow, and in a spray of precious stone flickers on a snow-covered driveway. Some halos last all day, yet rare arcs come and go in a matter of minutes. I figure on average I see some form of halo every 3 days, a lifetime total so far of about 8000.
In addition to the subtle variations in the extra arcs below the rainbow’s violet curve, coloured rings around the Moon, and the wide range in ice crystal halo forms, Greenler takes the reader through the play of light in clouds, the red of the sunset, and the purples in the belt of Venus shortly after. He finishes off with the mechanics of mirages, the twinkling of stars, and the formation of the famous green flash.
Follow this up (or start) with Marcel Minnaert’s “The Nature of Light and Color in the Open Air”. You won’t believe the number of marvellous things happening all around you that you’ve never noticed before. The more you know, the more you see. What a fantastic universe we live in, and it’s all the better when you get a buzz from appreciating every little lick and flicker of light.