We All Know Rainbows But Have You Ever Seen a Moonbow – A Night Rainbow Lit By the Moon?

A moonbow (also known as a moon rainbow or lunar rainbow) is a rainbow produced by moonlight instead of direct sunlight. Apart from the light source, its formation is no different from that of a solar rainbow: it is created by light being reflected in water droplets in the air caused by rain or a waterfall, for example. They are always positioned on the opposite side of the sky from the Moon relative to the observer.

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Mentioned at least since Aristotle's Meteorology (circa 350 BC), moonbows are much fainter than daytime rainbows, since the surface of the Moon reflects a smaller amount of light. For this reason, it is much more difficult for the human eye to discern colors in a moonbow, as the light tends to be too dim to activate the color receptors in our eyes. As a result, we usually see moonbows to be white, but their colors do appear in long exposure photographs. A 10pm blood red night rainbow over Scotland! Image credit: Stefan Lee Goodwin