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    Re: Position from altitude and azimuth.
    From: Bill Lionheart
    Date: 2020 May 19, 14:19 +0100
    I rearranged Flexner's formula and plotted an example with 45 degrees as the angle and the longitude of the star as 80 degrees.   It is close to
    a circle but as you tilt it you see it goes out of the plane. I also calculated the curvature and torsion of the curve (in Mathematica as it was complicated)
    The result is the curvature is close to a constant and the torsion is small but varies.

    Frank's diagram really helps me to understand when and why  you get two solutions to the alt azm  fix problem. And for a wide range of parameters the isoazimuth does look like a small circle.  But it is only a limiting case.  We see also that in a small circle the angle subtended by the great circles to either end of a chord is not constant.

    Bill

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