Photographic observation of a natural fourth-order rainbow

Appl Opt. 2011 Oct 1;50(28):F129-33. doi: 10.1364/AO.50.00F129.

Abstract

We report what is believed to be the first photographic recording of a quaternary rainbow in nature. It appears on the Sun side of the sky with its red arc at a radius of about 45° from the Sun. The original pictures have been subjected to various forms of image processing to reveal the tertiary rainbow as well as the quaternary rainbow, which are separated by only a few degrees with their colors reversed and their red arcs adjacent to each other.