Sunday, November 12, 2017

Mystery Halo

Last Saturday I was out in the yard, chasing a Great Blue Heron that Patty had spotted out the living room window. She said it was headed toward the back pond. Alas, it was not there (which I suppose is a good thing).

As is my habit, I looked up. And saw this.

Look closely left of center in the wispy clouds and you can see the hint of a rainbow like arc. (As always, click on any image to bigafy it.)

Here is a closeup of that area.

I had a camera, actually two with me, but neither had the right focal length lens for the scene. I had a zoom telephoto on my DSLR to shoot the heron. And I had my iPhone. I needed a wide angle lens on my DSLR. But as these atmospheric phenomena are often fleeting, I had to use what I had.

The mystery comes from the geometry of the situation.

The shot above shows the halo fragment, center left, and the Sun, lower right, through the trees. Using the tools I had at hand (pun!) I measured the angle between the sun and the arc, and it was over fifty degrees. This meant it was not a fragment of the 22° nor 46° halos. And it was not a circumzenithal arc as it was not at the zenith.

So I next headed over to Atmospheric Optics, but the answer was not obvious. So I emailed the proprietor of that fine site, Dr. Les Cowley, and he was kind enough to respond. He thinks it might be a fragment of a Supralateral Arc. He also noted that the wispy clouds were likely Ice Crystal Fall Streaks from Hole Punch Clouds.


I've seen punch clouds before, but this is my life Supralateral Arc. Very cool.

Keep looking up!

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