by Kevin Burton
Would you believe? Rainbows by night; moonbows!
They’ve got to be good looking ‘cuz they’re so hard to see. But they do exist. Poets, take note.
Never heard of this, but this week I read about them on interestingfacts.com, then on Wikipedia. I say, there must be a song in there somewhere. “Moonbow Molly and that night in Santa Fe” or something like that.
“A moonbow (also known as a moon rainbow or lunar rainbow) is a rainbow produced by moonlight rather than direct sunlight,” according to Wikipedia. “Other than the difference in light source, its formation is the same as for a solar rainbow. It is caused by the refraction of light in many water droplets, such as a rain shower or a waterfall, and is always positioned in the opposite part of the sky from the Moon relative to the observer.”
“The sun is the most reliable way to create the gorgeous light display we call a rainbow, but it’s not the only way,” writes Interesting Facts. “After all, the moon illuminates the Earth, too – and rainbows are essentially an optical illusion caused when water droplets split light into its ROY G. BIV components.”
“But seeing a moonbow isn’t exactly easy. How rare is this nighttime meteorological phenomenon?”
“Well, Aristotle wrote around 350 BCE in his treatise Meteorological that “it was formerly thought that (rainbows) never appeared by night as a moon rainbow. This opinion was due to the rarity of the occurrence…we have only met with two instances of a moon rainbow in more than fifty years.”
“So, pretty rare. That’s because for a moonbow to form, you need a variety of conditions to be Goldilocks-level perfect,” Interesting Facts writes.
“First, the moon must be low in the sky, and can’t exceed 42 degrees from the horizon. The moon must be full or near full, and you can’t be hanging around any artificial light – sorry, no moonbows in cities.”
(No moonbows in cities? OK, correction to song idea: “Moonbow Molly and that night in a shack set way back off a country road 19 miles from Santa Fe, with our dog Aristotle.”)
“Finally, just like rainbows, moonbows need water droplets in the atmosphere, so waterfalls are often a good spot to go hunting for moonbows. Just don’t expect to see the dazzling array of color typical of a daytime rainbow. Because the moon isn’t as bring as the sun, less light is refracted, and a moonbow usually looks white (at least to human eyes). But if you have a camera handy, long-exposure photos will reveal a moonbow in all its colorful glory,” Interesting Facts wrote.
For moonbows to be visible, “the night sky must be very dark,” according to Wikipedia. “Since the sky is not completely dark on a rising/setting full, moon, this means they can only be observed two to three hours before sunrise (a time with few observers), or two to three hours after sunset. And of course, there must be water droplets (e.g. from rain or spray) opposite the Moon.”
“Moonbows may also be visible when rain falls during full moonrise at extreme latitudes during the winter months when the prevalence of the hours of darkness gives more opportunity for the phenomenon to be observed,” according to Wikipedia.
“It is said that the definition of the colors depends on the size of the moisture drops present in the air; the smaller they are the less vivid the colors. Below 1/500 inch diameter they usually refract more or less white light as the component colors are merged.”
“Numerous places in the world produce spray-, fog- or mist-induced bows. In the United States such bows may be seen in relation to various waterfalls including Niagara Falls, New York, Yosemite National Park, California, and Cumberland Falls, near Corbin, Kentucky.”
“Victoria Falls, on the border between Zambia and Zimbabwe is also widely known for spray moonbows.”
“Spray moonbows are also seen with some regularity in the cloud forests of Costa Rica, in mountain towns like Monteverde and Santa Elena. These occur when clouds of mist are blown in from the Caribbean by the Christmas Winds.”
“The Christmas Winds happen from the end of December through late January or early February. These clouds of mists create a streaming pattern of stripes giving rise to their popular name in Spanish, pelo de gato (“cat’s hair). Moonbows happen in this part of Costa Rica almost every full moon in the months of December through February. The bows that are caused by Pelo de Gato are not limited to just before dawn but can happen after sunset too, but it does need a full or nearly full moon.
“Moonbows are also found in wet regions of Hawaii, such as Kauai (with the moon rising in the east during light rain) and the Big Island of Hawaii.”
So be on the lookout for moonbows, and for my hit song about Moonbow Molly and that night in Costa Rica.
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