Re: pinhole Solar halos

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From: pauld@exploratorium.edu
Date: Wed Jun 05 2002 - 09:49:35 PDT 

Message-Id: <200206051649.g55GnWp14878@isaac.exploratorium.edu>
From: pauld@exploratorium.edu
Subject: Re: pinhole Solar halos
Date: Wed, 5 Jun 2002 09:49:32 US/Pacific

Hi Ben

I saw the same display from Windy Hill above Half-Moon bay.

I believe the outer halo was a colored arc about half way between the 22.5 degree
halo and the horizon and was also a circumhorizontal arc. A nice one too.

As I hiked down the hill I put on my teacher hat and pointed out the bright halo
to everyone on the trail. Most hadn't seen it.

To those that responded that they had noticed the very bright halo I pointed out
the colored band of the circum horizontal arc. Most people stopped and watched
the display for quite a while. They then started asking questions about what
caused it.

Then on the display this Sunday my wife Ellen, who is a great observer, pointed
out the parhelic circle to me.

Paul Doherty science-teacher-at-large

> About a week ago (+/-) we saw halos around the sun here in Half Moon Bay. About 20
degrees sounds right. (not having measured it, I'll take the word of the
experts) In
addition, there was a second, dimmer halo, at about double that angle. The inner
halo was
easily visible with the naked eye (with fist covering the sun - emphasized for
the 10-yr
old with us). The outer halo was less intense; much more difficult to see. We
were more
able to see (parts of) the outer halo with sunglasses that are polarized.
>
> We then discussed the difference between this and a rainbow, where the sun is behind the
observer, and the different altitudes of the two phenomena. The ice crystals
usually are
higher. (The necessary ice crystals tend to be at higher altitudes than the
droplets that
form rainbows) The halos are more similar to moon rings than to rainbows, unless
I'm
mistaken.
>
> I love how 10-yr olds are often very fascinated and intense about observations, but for
a
very short time. I mused about the halos for awhile, but she was off on other
explorations in no time at all! But she remembers these things and surprises us
all the
time by remembering little details.
>
> Ben
>
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