The Moon Bow

OFF THE BEATEN PATH
An adventure of few locations on planet earth where you can
see the “MOONBOW”…
In the late 1700s, English poet William Cole put his description
of a Moonbow into verse:
The atmosphere with humid vapors flow/ And the moon displays
her lunar bow.

If you would like to experience an adventure that few have the
opportunity to enjoy, you may wish to view the “moonbow” at
Cumberland Falls, near Corbin, KY.
What is a “moonbow”? Moonbows, or lunar rainbows are
rainbows produced by moonlight rather than direct sunlight and
are rare natural atmospheric phenomena that occur when the
Moon’s light is reflected and refracted off water droplets in the
air. They are much more rare than rainbows because a variety of
weather and astronomical conditions must be just right for them
to be created. They are much more faint 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. This is why a moonbow often
appears to be white. However in long exposure photographs the
colors in a moonbow do appear.

Moonbows are more easily
viewed when the Moon is
at or nearest to its brightest
phase full moon. The moon
must be low in the sky at
an elevation of less than 42
degrees or lower, and must
not be obscured by clouds.
Also, the night sky must be
very dark. The sky is not
completely dark on a rising/
setting full moon so moonbows
can only be observed
two to three hours before
sunrise, or two to three
hours after sunset. Also,
there must be water droplets
from rain or spray opposite
the Moon.

These requirements
make moonbows
much more rare than rainbows produced by the daytime sunlight.
Moonbows may also be visible when rain falls during full moonrise
at extreme latitudes during the winter months when darkness
is more prevalent.
It has been stated that the definition of the colors depends upon
the size of the moisture drops present in the air: the smaller they
are, the less vivid the colors. Below 1/500 in diameter they usually
refract more or less white light as the component colors are
merged.
Numerous places in the world feature spray, fog, or mist-induced
bows. In the United States such bows may be seen in relation to
various waterfalls including Niagara Falls in New York, Yosemite
National Park in California, and Cumberland Falls near Corbin,
KY, and Victoria Falls, on the border between Zambia and Zimbabwe
is also widely known for spray moonbows.