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    Re: Nav Exercise #4- Amplitude of the Sun
    From: Peter Fogg
    Date: 2008 May 25, 09:54 +1000


    On Sat, May 24, 2008 at 5:47 PM, Anabasis <jcaoy@yahoo.com> wrote:

    Here is an example of one of those archaic amplitudes.

           A ship is at sea and its DR Latitude is 14 degrees North.  At about
    0830 UTC on 6 May 2008, an amplitude of the sun is observed while the
    body is on the celestial horizon giving a bearing of 288.0 deg per
    gyro compass.  Local variation is 2.0 deg East.  The ship is heading
    208 deg per gyro compass and the magnetic compass heading is 207
    degrees.  Determine Magnetic Compass Error, Gyro error, and Deviation
    at that heading.    Please let us know if you used tables or formula
    to find the amplitude value.

    Jeremy
     
    Not much time right now for matters navigational, but couldn't resist having a quick look at an amplitude.  Via a somewhat crude method, using tables for another purpose, have calculated amplitude at between 17d and 18d.

    Since at sunset azimuth = 270d + amplitude N, - amplitude S, the derived azimuth becomes about 287.5d.

    My text advises:
    "To observe the altitude close to zero, the Sun should be observed when the lower limb lies about a semi-diameter above the horizon, and the Moon when the upper limb touches the horizon - at the time of appearing and disappearing".


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