You All Know Rainbows But Have You Ever Witnessed A Moonbow – A Night Rainbow Lit By The Moon?

Moonbows which are rather different from rainbows are also known as lunar rainbows. They differ from the average rainbow that we know and are created by the shimmers of the moon rays instead of the sun rays.

Image source: Stefan Lee GoodwinA 10pm blood red night rainbow over Scotland

Its formation is no different apart from the light source. Similar to the occurrence of a rainbow, the moonbow is also created by the reflection of light in water droplets present in the air, but in the presence of moonlight. However, these moonbows are usually positioned opposite from the Moon relative to the observer.

Details of moonbows have been mentioned in Aristotle’s Meteorology (circa 350 BC) too. The moonbows are much fainter than the rainbows that occur during the daytime as the moon only reflects a smaller amount of light. Therefore, it's quite difficult to discern the colors in a moonbow for a human. The light reflected is too dim to activate the color receptors in our eyes. Thus, the moonbows appear to be white. But still, we'd be able to see its colors in long exposure photographs.

Image source: Arne-kaiserLunar rainbow over Kihei, Maui, Hawaii, US

Moonbows are best visible when there's a full moon. The moon should be in one of its brightest phases and should not be obscured by clouds for the best view. And also, the moon must be low in the sky at an elevation of less than 42 degrees at least. Plus, the night sky should be completely dark. Even though the sky is not at all dark during a full moon; the moonbows can be observed for two or three hours after the sunset.

These requirements are those that make moonbows quite rarer than rainbows. The possibility for the occurrence of a moonbow is less than 10% as often as rainbows. In some instances, moonbows can be observed during full moonrise during the months of winter when rain falls at extreme latitudes. However, the definition of the colors depend on the size of the water drops. The smaller the moisture drops are the less vivid the colors will be.

Image source: GarryA night rainbow on Fraser Island, Queensland, Australia

Moonbows are often induced by fog, spray and mist apart from rain. Such bows can be noticed around various waterfalls in the USA including Niagara Falls, New York, Yosemite National Park, California, or Cumberland Falls, near Corbin, Kentucky. Moreover, Victoria Falls, on the border between Zimbabwe and Zambia is also well-known for spray moonbows.

Image source: CalvinBradshawA spray-induced moonbow (lunar rainbow) at Victoria Falls (Zambia side)

As mentioned earlier, moonbows can be seen for only about 3 hours around the full moon during the end of evening twilight or before sunrise. Summer can be identified as the best time for long lasting moonbows as the moon spends more time in the lower sky. Moonbows may last only up to a maximum of one hour during other seasons.

You can also try to find a quite pale moonbow in showery weather. Though you won't see many colors in it with your naked eye, you'd definitely be able to witness the colors if you capture it by mounting a camera on a tripod.

Image source: Terje Nesthus

So, make sure to try to capture a Moonbow. Stay tuned for more interesting stuff!

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