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Sun Dogs



The last couple of days I've been noticing great "sun dogs". Winnipeg
is a good place to see them, but these have been great. They have been
full "rainbow" colored (red inside, blue outside) arcs on either side of
the sun, making up approximately a third of a full circle. I realized
that my textbooks don't address this, but I'll be doing optics in the
new year and I thought they'd provide an interesting example. I haven't
come up with a ray diagram myself yet, but there appears to be a bit to
these as the page http://www.gi.alaska.edu/ScienceForum/ASF0/036.html
refers to the effects - particularly the viewing angle of 22 degrees -
relying on the ice crystals having hexagonal faces.

Does anybody know a bit more about these? My other observation is that
they appear to the left and right of the sun and can be extremely bright
when roughly parallel, making me wonder if polarization is an important
consideration.


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Doug Craigen
Latest Silliness - the Mark of the Beast Calculator
http://www.escape.ca/~dcc/beast/?3