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    Re: Accuracy of the Time Sight
    From: Gary LaPook
    Date: 2012 May 20, 12:43 -0700
    Except that the LHA and hence the longitude determined with the time sight depends on the latitude used in the computation and errors introduced by inaccurate latitude are reduced with the body on the prime vertical.

    gl

    --- On Sun, 5/20/12, Paul Pauliukonis <kb1ty.rimas---.com> wrote:

    From: Paul Pauliukonis <kb1ty.rimas---.com>
    Subject: [NavList] Accuracy of the Time Sight
    To: NavList@fer3.com
    Date: Sunday, May 20, 2012, 11:59 AM

    Ever since being informed of the Time Sight - using the sextant as a sundial, I became curious of the accuracy to be expected from this type of observation.

    In order to determine the variance between the exact longitude of the observer and the longitude calculated by the Time Sight, I modified my program (written for practicing sun sights and containing high accuracy solar almanac) by adding a subroutine which used the calculated altitude of the sun (Hc) to calculate LHA and obtain LMT. Since the same equation is used to calculate both values, the theoretical variance should be zero. My interest was to see if other factors (besides Eqn-of-Time) affected the "zero value" and by how much. Enclosed graph shows the results of this calculation. I chose 21 June 2012 as the date in order to obtain the maximum range for the azimuth of the sun.

    The results surprised me. I think that the recommendation in Bowditch(1906) of taking Time Sight near the Prime Vertical has more to do with the rate of change in sun's altitude than with the accuracy of the LHA.


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