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    Re: Checking compass deviation
    From: Franklin H Norris
    Date: 1995 Aug 24, 14:28 -0500

    What you need to calculate is the amplitude of the sun.  Amplitude
    is the true bearing of a rising or setting body measured north or south
    of due east or due west.
    The formula is
        Sin(Amplitude) = Sin(Declination)/Cos(Latitude)
    Amplitude is north for north declination and south for south declination.
    For example: if the sun's amplitude is 10.2 degrees north and your
    latitude is 40 degrees north then the amplitude is 13.4 degrees north.
    This means the sun will rise with true bearing 90-13.4 or 76.6 degrees.
    Likewise, the sun will set with true bearing 270+13.4 or 283.4 degrees.
    If the moon's declination is 7.75 degrees south and your latitude is
    20 degrees south, the amplitude is -8.2 degrees or 8.2 degrees south.
    This gets tricky.  Since the declination is south, the moon rises
    at 90 - Amplitude degrees.  The amplitude is -8.2 so the bearing
    is 90 - -8.2 = 90+8.2 = 98.2 degrees.  The moon will set at
    270 + -8.2 or at 261.8 degrees.  This happens on September 7 of this
    South declination always results in the phenomenon occurring south of
    due east or west.  When the declination of the body is north, it rises
    and sets north of due east or due west.
    Good luck adjusting your compass.

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