Ben's Photo Blog

Photos from my various adventures

A Lunar Treat

Posted by Ben on December 2, 2009

I got a call last night, around 11, while I was working on my take-home test for Real Analysis.  It was my friend Caleb calling to tell me to come outside and look at the moon, and to bring my camera.  I didn’t really know what was going on at the time, but I figured I could use a break, so I grabbed my camera bag and headed out the door.  I found him outside, staring up at the sky.  Following his gaze, I was able to make out a ring around the moon.  We headed out to the middle of the drillfield, where it was marginally darker, to get a better look, and here’s what we saw:

This was taken with a 15 second exposure, shorter ones didn’t really capture much of the ring.  I’d have to say that this ranks up there as one of the coolest things I’ve ever seen in the night sky.  The name of this phenomenon is the 22° halo.  You can read more about it here if you’re interested.  Basically, the ring is formed when the light reflecting off of the moon is refracted through hexagonal ice crystals present in high, thin, cirrus clouds.  I think one of the coolest aspects of this is that the disk between the moon and the halo is so much darker than the surrounding sky, another phenomenon known as an Alexander’s Band.  The first thing that pops into my head is that it looks like a giant clear sphere with a single light source floating in the middle of it.  Because of the way the ice crystals refract the light, you may be able to make out different colors in the ring.  Once we noticed that, I zoomed in on the bottom edge of the ring to see if they would show up more clearly without as much light from the moon:

It’s pretty easy to pick out all of the colors of the rainbow here, with the red on the inside of the ring and the violet on the outer edge.

-Ben

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One Response to “A Lunar Treat”

  1. Breathtaking — surpassing surreal.

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