Moonlight Circumzenithal Arc by Lauri Kangas (photon-echoes) Ontario, Canada October 13, 2008. ©LauriKangas.

"I went out to check the skies after dark and saw the brightest lunar CZA that I have ever seen. I was amazed at the colours in the photo. There is absolutely no processing of the image other than size scaling."

CZAs have intense colours. Near parallel moonlight has entered the top faces of ice plates to be refracted through a 90° prism.