Lunar corona

  Three 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 Lauri Kangas.