Wednesday, November 24, 2010

Circles in the Sky

As I was driving back form Connecticut (see future post) and stuck in brutal Thanksgiving Traffic I was treated to a wonderful halo display. Fortunately I was able to pull into a parking lot and get some pictures. Alas it wasn't until the display had faded a bit.

I was still able to get a nice shot of a 22˚ halo with a matching pair of sundogs (as always, click the image for bigification).

The first image has a hint of the upper tangent arc, while it is a bit more apparent in this image. The sundogs on the other hand have faded a bit.

Since I was stopped I decided to use the facilities in the fast food place located conveniently nearby. When I came out I noticed that what I thought was the upper tangent arc had brightened considerably.  Although it had dimmed by the time I retrieved my camera for this shot. But the upside down rainbow center top of this image is not the upper tangent arc. It is instead a circumzenithal arc. And it is on the 46˚ halo, a somewhat rarer beast then the 22˚ version.

This isn't a very good image, and even when viewing the full sized version (you did remember to click the image) the outer halo and arc are subtle at best (it is most obvious on the left). I didn't realize that I'd mistaken the 22˚ for 46˚ halo until I looked at the images on my computer at home.

(The key lesson here is not to give up on the display to soon, as the clouds and accompanying circles, can change rapidly. I'll be ready next time (yeah, sure).)

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