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    Longitude by Time Sight...good enough at sea?
    From: Doug MacPherson
    Date: 2012 Nov 21, 13:27 -0800


    I recently was reading the posts on 10 nm accuracy being good enough when fixing your position at sea, far from any land mass.

    I recently taught my self the Time Sight method of computing Longitude (using an assumed latitude) from an 1938 copy of Bowditch using the haversine tables found in Table 34 of Bowditch. This seemed to be the normal procedure prior to the distribution of Ho 229 and others.

    Not a lot of computation involved and you can plot your fix directly onto the chart.
    I consistently get within 5 NM of my actual position when shooting from land..all be it, with the correct Latitude, but varying the Latitude by a few nm keeps me within the 10 nm.

    Any reason why traditional sailors travelling the seas would not use this method when far from land today when they are inclined to turn off the GPS?

    In Northern climes....Get your lat. from Polaris in the morning.....Take a time sight just after the sun has risen (best accuracy when sun is near the prime vertical) using you assumed Polaris Lat carried forward.....Get your lat. at noon from the sun...and then another Long. prior to the sun setting with your assumed Lat worked from your noon sight.

    Would seem to save a lot of plotting.


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