MOONBOW : A Beautiful Night Natural Phenomenon

What is moonbow?

A moonbow (also known as a lunar rainbow or white rainbow), is a rainbow produced by moonlight rather than sunlight. Other than the difference in the 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. 

Moonbows are much fainter than solar rainbows, due to the smaller amount of light reflected from the surface of the moon. Because the light is usually too faint to excite the cone color receptors in human eyes, it is difficult for the human eye to discern colors in a moonbow. As a result, a moonbow often appears to be white. However, the colors in a moonbow do appear in long exposure photographs.

Moonbows have been mentioned at least since Aristotle's Meteorology (circa 350 BC).

                        

Where is it found?

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, in Africa on the border between Zambia and Zimbabwe and Plitvice Lakes in Croatia 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. Moonbows are also found in Kauai, Hawaii, with the moon rising in the east during light rain.

How does it form?

The moon can create rainbows if the light that reflected is bright enough and there's sufficient moisture in the right spot in our atmosphere.

Our moon must be nearly full in order to provide enough light for moonbows to form. Even as a full moon, our natural satellite doesn't provide nearly as much light as the sun.

The light that is sent from the moon toward our atmosphere refracts, or bounces, through droplets of rain. This light is separated at different angles in the raindrop, like a prism into multiple colors, where warmer colors like red and orange correspond to longer wavelengths and cooler colors such as blue and purple correspond to shorter ones.

If the droplets are too small, like in fog or mist, the colors are less able to separate completely and a white or gray fogbow will form. Fogbows can form overnight if there's enough moonlight and moisture in the air. 

Viewing?

Moonbows are most easily viewed when the moon is at or nearest to its brightest phase full moon. For moonbows to have the greatest prospect of appearing, the moon must be low in the sky (at an elevation of less than 42 degrees, or lower) and must not be obscured by cloud. 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 , or two to three hours after sunset. And, of course, there must be water droplets (e.g. from rain or spray) opposite the moon. This combination of requirements makes moonbows much rarer than solar rainbows.

                                            (ooo... its fainter than solar rainbows!) 

It is very rare to found and see the moonbow, so if you have the chance, take your best pic of it! 

source : wikipedia and weather.com