rings surround the central aureole of this lunar corona imaged by
Lauri Kangas (site)
on 31st January 2004. The three quarter moon is not visible because
of the necessary overexposure needed to capture the coronal rings.
"Tonight, while I was shoveling snow I noticed a really distinct
corona around the moon. The temperature was -8C and the wind was really
cold and blowing fine dusty snow around. I think coronae are usually
caused by water droplets but it was way too cold for liquid water,
at least at ground level!" Coronae are formed by
ice crystals, supercooled water droplets might also have been present.
Whatever created it, a corona of this exceptional finesse required
very uniform droplets or particles. Image ©2004