[Brian received some lovely photos of Moon Rings from Richard Youden… see LETTERS]
Yes … this phenomenon is, as you say, nothing to do with how far away from the Earth the Moon happens to be. All that stuff was greatly over-hyped, by the way, of course … the moon was not significantly differently placed from where it’s been for the last 10,000 years!
These beautiful circles are ICE-BOWS. They are caused by something much closer to home – the Earth’s atmosphere, through which we are always observing the sky, when we stand on the Earth’s surface. In this case we are seeing refraction by ice crystals suspended in the air above us – usually at about the same height as those ‘paint-brushed’ Cirrus clouds we often see when the sky isn’t covered with the lower-level rain clouds. It’s the same kind of thing as a Rainbow .. in that we only see a refracted beam of light if the angles are exactly right – and that happens anywhere in a particular circle around the Moon, and nowhere else – hence the well-defined bright ring. The funny thing is … these rings must surround every celestial light source .. not just the moon – so if our eyes were much more sensitive, we would see rings around every star! Like ripples in a pool …
Well, it would be interesting to try to detect them!
By the way … Richard’s two pictures, with a little colour and intensity adjustment, make a very pleasant stereo image ! The clouds and Moon moved just the right amount in the right direction.