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    Re: Time sight primer
    From: David C
    Date: 2019 Sep 26, 21:42 -0700

    Frank Wrote

    First, many navigators were still doing longitude by time sight as late as the Second World War. The history of navigation is more varied than the cartoon histories in the navigation manuals (Bowditch, e.g.) would imply. Next, the expression "longitude by chronometer" was British "slang" for what we call a time sight today. So that's the same thing really. In the 19th century, these were often called sights "for the true time" by which they meant local apparent time... Sun time was "true time". As for UTC, it's only trivially different from GMT, and navigators depended on that from the late 18th century onward.

    Frank makes it clear that primaty sources should be used, not navigation text books. I do not have any of the former so am forced to rely on textbooks............

    Practical Navigation for Second Mates (T G Jones 1955)  states that

    In the MOT examination, either the Longitude method or the Marc St Hilaire method  can be used.

    The book then gves examples of each method. The inference is that in the British merchant service the longitude method was still being examined in the 1950s. Maybe the method was still in the exams at the start of the GPS era but I do not have any proof.

    HS Blackburne, who wrote  several navigation treatises, was Examnier of Masters and Mates to the NZ Government. In the archives there is correspondance in which he refers to sending sealed packets of exam papers around the country. Unfortunately none of the packes have survived - probably for obvious reasons. On at leat one occarion Blackburne had to deal with cheating by a candidate.

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