Interesting Facts About Moonbows: Rarer Than Rainbows

Moonbow

Moonbow

Moonbows (also referred to as a white rainbow or lunar rainbow) are rare natural atmospheric phenomena, which occur when the Moon’s light is reflected and refracted off water droplets in the air. Other than the difference in the light source, its formation is the same as for a solar rainbow.
Unlike a solar rainbow that sunlight produces, a moonbow is a rainbow produced by moonlight. The refraction of light in many water droplets, such as a waterfall or a rain shower, and is always positioned on the opposite side of the sky from the moon relative to an observer causes moonbows.
Moonbows are much fainter than solar rainbows because of the smaller amount of light reflected from the moon’s surface. That is why a moonbow usually appears to be white. However, the colors in a moonbow appear in long exposure photographs. Since the light is usually too faint to stimulate the cone color receptors in human eyes, it is quite difficult for the human eye to discern colors in a moonbow. Moonbows have been cited at least since Aristotle’s Meteorology (circa 350 BC), and in an 1847 publication as well.
The following are FIVE interesting facts about moonbows. Hope you enjoy!
1. For moonbows to have the highest prospect of appearing, the night sky must be very dark, and the moon must be low in the sky (at an elevation of less than 42 degrees, preferably lower). Of course, there must be several water droplets (rain showers or waterfall) falling opposite the moon. You can easily view Moonbows when the moon is at or nearest to its brightest phase full moon. Since the sky isn’t entirely dark on a rising/setting full moon, it means that you can only observe them two to three hours before sunrise (time with few observers), or two to three hours after sunset. The combination of these requirements makes moonbows much rarer than rainbows that sunlight produces.
2. One perfect location for viewing ‘true moonbows’ is Waimea ‘Kamuela,’ Hawaii Island, Hawaii. You may also view moonbows when the rain falls during the full moonrise at the extreme latitudes during winter months. The prevalence of the darkness hours during winter provide more opportunity for one to observe the phenomenon.
3. Several places in the world feature spray-, fog- or mist-induced bows. In the United States, you may see such bows in relation to different waterfalls including Cumberland Falls, near Corbin, Kentucky and Yosemite National Park, California. Plitvice Lakes in Croatia and Victoria Falls, in Africa on the border between Zambia and Zimbabwe are also widely known for spray moonbows.
4. Spray moonbows occur when Christmas Winds blows in the clouds of mist from the Caribbean. The Christmas Winds occur from the end of December through late January or early February. These clouds of mists form a streaming pattern of stripes; thus, giving rise to their popular Spanish name: Pelo de Gato (meaning Cat’s Hair). Spray moonbows are also seen with some regularity in the Costa Rica cloud forests, in mountain towns like Santa Elena and Monteverde. Moonbows occur in this part of Costa Rica almost every full moon in December through February.
5. You can also find moonbows in Kauai, with the moon rising in the east during a light rain. Since they appear white to the naked eye of many people, you must capture them with a time-exposure photo. You can occasionally see similar bows from Kohala districts on the Big Island of Hawaii and Velasco Lemery Iloilo Philippines. Pelo de Gato causes moonbows that aren’t limited to only before dawn, but they can occur after sunset as well. However, it needs a full or nearly full moon.

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