A lunar rainbow, also known as a moonbow gave wonder to the sky over Iceland.
What is a moonbow? According to Texas State University: A moonbow (also known as a lunar rainbow or white rainbow), is a rainbow produced by light reflected off the surface of the moon (as opposed to direct sunlight) refracting off of moisture laden clouds in the atmosphere. Moonbows are relatively faint, due to the smaller amount of light reflected from the surface of the moon. They are always in the opposite part of the sky from the moon.
Because the light is usually too faint to excite the cone color receptors in human eyes, it is difficult for the human eye to discern colors in a moonbow. As a result, they often appear to be white. However, the colors in a moonbow do appear in long exposure photographs.
Conditions must be ideal for moonbows to form. A bright moon and abundant water droplets suspended in clear air in opposite directions from the viewer and because of this rarity, few people have ever seen one.
— Víðir Björnsson (@vidirb) November 22, 2015
Image: Víðir Björnsson @vidirb