A rainbow is cause by the sun shining o moisture droplets, most commonly after a rainstorm. Rainbows contain many colors and are the most common.
The moon is the key, just as sunlight produces rainbows during the day, moonlight can produce rainbows at night. This is a lunar rainbow or 'moonbow'.
Moonbows are rare because moonlight is not very bright. A bright moon near to full is needed, it must be raining opposite the moon, the sky must be dark and the moon must be less than 42ยบ high. Put all these together and you do not get to see a moonbow very often! "To the unaided eye they usually appear, as in the small image, without colour because their light is not bright enough to activate the cone colour receptors in our eyes. Nonetheless colours have been reported and might be seen when the moon is bright."
Moonbows are rare because moonlight is not very bright. A bright moon near to full is needed, it must be raining opposite the moon, the sky must be dark and the moon must be less than 42ยบ high. Put all these together and you do not get to see a moonbow very often! "To the unaided eye they usually appear, as in the small image, without colour because their light is not bright enough to activate the cone colour receptors in our eyes. Nonetheless colours have been reported and might be seen when the moon is bright."
It is very common for a moonbow to form over a waterfall, as shown in your picture, because of the high amount of moisture due to the fall. I also found out that you can't actually see the colors like you said, but can be captured by long exposure photography.
ReplyDeleteMoonbows are also know as Lunar Rainbows, Lunar Bows, or White Rainbows. They are rare because it's the result of light reflecting off the surface of the moon instead of direct sunlight. They are normally very faint because the light is very dim. They always occur on the opposite side of the sky where the sun is.
ReplyDeleteA real Moonbow is white, and lit from the moon alone. A colored rainbow when the sun is setting or when it's just turning dark isn't a true Moonbow because it's still light outside. Moonbows occur in very few places, but many sightings have occurred in Cumberland Falls, Kentucky
The colored circle you see sometimes around the moon IS NOT a Moonbow. It's a 22 degree halo, caused by refraction in hexagonal ice crystals in cirrus clouds. Colored rings are a diffraction phenomenon.