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    Re: Chronometers
    From: Jean-Philippe Planas
    Date: 2008 Mar 26, 14:53 -0700
    Yes Alex, please tell us about the story of purchasing the chronometer from Russia.

    alex <eremenko@math.purdue.edu> wrote:

    Dear list members,
    I think that of all (archeo)-navigation topics, chronometers were not
    on this list in all detail.
    I recently purchased one (a late Soviet one), and I have many

    1. In the general books about chronometers (NOT the navigation books)
    they say that it is not important that a chronometer shows "exact
    The important feature is the "constancy of rate". For example, if a
    shows 24 hours and 1 second for each 24 hours period, this is a good
    because you can have an easy correction formula:
    True time=(Chronometer time) minus (the number of days since the last
    checkong) seconds.
    My question: what was the normal practice in XIX and early XX century.
    Did they routinely determine the daily rate and then used a linear
    correction formula
    True time=(chronometer time) plus (the daily rate) times (the number
    of days since the last checking) plus constant?

    Or they just tried to regulate a chronometer to have zero daily
    deviation and then used
    the time it shows as the true time? Somehow I cannot find the answer
    in the navigation manuals
    and even in Chauvenet.

    2. Since I bought my chronometer, I put it on test, that is I wind it
    regularly and check against
    a good electronic watch. (The electronic watch I check every month
    against GMT on the internet).
    The experiment (which is running for about 1 month already) shows that
    the chronometer is
    slow by 1.4 seconds every day in the average, and if I add this
    correction, the chronometer
    time is accurate within 1 second most of the time. Is this a good

    The factory certificate says that the maximal daily "going" has to be
    at most 3.5 sec, and
    this particular one showed 1.3 seconds on the factory test.

    3. There was a funny story of purchasing this chronometer (from
    Russia) which I can tell if there
    is any interest:-)


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