Monday, 26 November 2012

mOOn HALO


           A lot of folks were buzzing about the nearly full moon last night and the clouds that were moving in front of the moons light. The clouds were VERY high in the skies, probably somewhere between 20000-30000 feet and were flowing our way from the big southern storm. On occasion what will happen, especially when the moon is full or close to it, is that a “ring” rill form around the moon. This ring is really called a halo and is a rather common sight in our skies, especially through the fall and winter season.
pic from my home

Sometimes if the clouds are moving through quickly and are sparse in coverage, the halo lasts for only a few minutes or has a tough time actually forming. Other times, like last night, when the stream of clouds is persistent, the halo fully forms and lasts for awhile.
MOON HALO under fluorescent light

from my friend's cam


OK so those are the beautiful pictures…but what exactly causes it?
As I mentioned at the top of the blog, high clouds, called Cirrus clouds moved through the region.  we often talk about these clouds being made from ice crystals. As the moons light passes through the crystals the light reflected and split up (refraction). If the crystals are oriented correctly and positioned just right, them boom you get a harmless “halo”.
Here is the cool thing, one person will see a halo, and if another person is a few miles away or more, since the clouds are oriented a different way, with respect to that person compared to the other person, the halo may look a bit different, and its possible the other person won’t even see a halo at all.
Can a halo happen with the suns light during the day…YES ?
A lot of folks were calling/emailing concerned about this phenomena…in reality it’s harmless and nothing to be concerned about. Oh and guess what the next full moon will be on 10/29…a couple of days before Halloween…who knows maybe Mother Nature will create a more spooky setting just in time for the holiday!