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    Re: Refraction at the horizon.
    From: Ken Gebhart
    Date: 2008 Mar 17, 21:04 -0500

    At the risk of bringing up "sun squash" again (new members can search
    the archives under this thread), I can state that data from 200
    photographs taken at sunset/ sunrise shows a 5% squash at 3 deg
    observed elevation at SL on Std day.  Sun disk images were projected
    on a wall and measured with a yardstick.  Maximum squash ever seen
    was 17%.  Distortion (squash) is more easily noticed with head at 90
    deg to the horizon than erect.  Don't ask me why.
    Ken Gebhart
    On Mar 16, 2008, at 4:32 AM, Marcel Tschudin wrote:
    > George wrote:
    >>  "I have often seen a highly distorted Sun disc, at altitudes of
    >> well over 3
    >>  degrees, that leads me to question it as a general rule."
    > Frank replied:
    >>  I'm going to doubt you on one detail here, George. Three degrees
    >> is six Sun
    >>  diameters. Now think back... have you REALLY "often" seen a "highly
    >>  distorted Sun" at six full Sun diameters away from the horizon??
    >> In my
    >>  experience, and yes, I DO look for these phenomena every chance I
    >> get, all
    >>  the action occurs at much lower angular altitudes.
    > I also was questioning George's observation. The only situation I
    > could imagine he is referring to is the situation of the sun being
    > partially covered by a thin cloud stripe. Different refractions at the
    > upper and lower edge of the cloud result sometimes in odd-shaped sun
    > images.
    > Marcel
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