The Science of Moonbows

Dumgoyach, via Wikimedia Commons

With National Moon Day approaching on July 20th and the Anniversary of the Apollo 11’s first landing on the Moon, we felt it appropriate to feature the science of moonbows in this month’s newsletter.

A moonbow is also commonly referred to as a lunar rainbow. A moonbow is a rare natural atmospheric phenomena that occurs when the Moon’s light is reflected and refracted off water droplets in the air.

Moonbows are much fainter than rainbows made by the sun and often appear to be white. This is due to the smaller amount of light reflected from the surface of the moon. The light from the moon is usually too faint to be perceived by the receptors in the human eye, it is difficult for the human eye to discern colors in a moonbow. However, the colors in a moonbow do appear in long exposure photographs.

A bright moon near to its brightest phase known as a full moon is needed in order to have a chance at seeing a moonbow. It must be also be raining opposite the moon, the sky must be dark and the moon must be very low in the sky (about 42º above the horizon). All these put together makes seeing a moonbow very special and rare!

There are some locations around the world where moonbows occur more frequently. Most of these locations tend to have waterfalls, which create layers of mist in the air. Some of these locations include Yosemite National Park in California and Cumberland Falls State Resort Park in Kentucky. Victoria Falls on the border of Zambia and Zimbabwe and Waimea in Hawaii.

Moonbow at Victoria Falls; By Scolopendra33 via Wikimedia Commons

Moonbow at Lower Yosemite Falls; By Brocken Inaglory via Wikimedia Commons

Moonbow over Kula, Hawaii; By Arne-kaiser via Wikimedia Commons



7 thoughts on “The Science of Moonbows”

  1. Yes I have seen a upside down moonbow, in Saratoga, N.Y.. It was a cold February night in the year 2000. There was a single cloud under the full moon that created an upside down rainbow in a starlight sky. I wish I had a camera at that point.

  2. I love these articles and stories about the moon and the clouds. I’ve always been fascinated by the awesome and amazing sky and all the cool things up there, but we didn’t have the internet when I was young, so it was rare that I got to read such fun and interesting stories like this. Everyday I learn something new, which is my favorite thing to do. Thank you.

  3. Was there a moon bow overlooking the Southwest around 1981,1982? I was living in Alamogordo, New
    Mexico during that time. I saw a very similar moon. The ring around the moon was mainly white. I was so mesmerized by it’s enormous size and beauty..

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