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    Re: Working Analemma
    From: Lu Abel
    Date: 2006 Nov 05, 16:51 -0800

    FrankReedCT@aol.com wrote:
    
    > One of the lecturers at the Seaport Planetarium at Mystic Seaport back
    > in the late 70s painted an analemma on his living room ceiling. He had a
    > mirror mounted on a little base on the windowsill of a south-facing
    > window. Once a week at exactly noon local mean time, barring clouds, he
    > would mark the spot on the ceiling where the Sun's image was projected
    > by the mirror. After a year he filled in an arc connecting the points.
    > Sure enough, he had that classic "figure eight" analemma shape (although
    > as Herbert Prinz has explained, it probably shouldn't be called an
    > analemma).
    
    Not sure I remember Herbert's post, but I assume it was because the
    shape was distorted?   At UPS, the figure-eight is severely distorted
    because the mirror from which the sun's light is projected is only 15
    feet away from the wall and 5 feet above the top of the "analemma."  The
    distance from the projecting mirror to the bottom of the analemma is
    over twice the distance from the mirror to the top of the analemma,
    leading to a significant distortion of its shape.  The UPS "analemma" is
    a stainless steel path about 2 inches wide, inscribed at about 10 day
    intervals.  It was constructed based on a set of plans provided by a
    professor who had to very carefully calculate the distortions induced by
    the location of the mirror.  Although it hasn't been in service for a
    full year, I hear it's doing fine so far....
    
    Anyway, it was neat to walk into a building and say "hey, I recognize
    that" when 99 out of 100 people on the street (and even well-educated
    college students) probably couldn't.
    
    Lu
    
    Lu Abel
    
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