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    Re: Chronometers
    From: Henry Halboth
    Date: 2008 Mar 26, 13:24 -0700

    Hi Alex,
    Congratulations on obtaining your new Chronometer.
    Generally speaking, the customary procedure was to
    keep an accurate record of the Chronometer Error
    (CE)by whatever means available to the navigator and
    to obtain from that record the daily rate, which was
    then applied to an observed time of observation in
    accordance with the formula you quote, adjusting the
    sign of total error application as necessary.
    I suppose there might be some argument with respect to
    methodology if the time between determination of
    errors was particularly great, such as might well be
    the case if Lunars or observations in a place of known
    Longitude or signal station time ball/flag be the
    method of error determination. In such latter cases it
    might not be proper to assume the rate to have been
    regular over the time interval, which, of course
    underscores to logic behind the importance of the
    predictability of a steady rate in a quality
    Since the advent of radio and radio time signals, it
    was customary to observe the CE daily at about the
    same time, which procedure, over a period of time
    reliably established a daily rate. I have a Hamilton
    USMC Chronometer, produced during WWII, or shortly
    thereafter, which I kept rated by daily radio time
    signals for many years and which consistently kept a
    daily rate of 1.5 seconds losing. From a practical
    point of view, it was customary to request a new
    chronometer be set slow so that the error be additive
    -I guess true sailors didn't subtract too well. It was
    also always considered appropriate to wind the
    chronometer daily at the same time, regardless of the
    actual run-down time and, on well run ships, to report
    that winding to the Master. The theory, right or
    wrong, was that the rate keeping ability was enhanced
    by using the same portion of the spring consistently.
    In my experience, at least, it was never considered
    appropriate to set a chronometer, and I have never
    seen a true chronometer that provided a setting
    mechanism other than by way of the center wheel stem
    which requires removal of the faceplate and use of the
    winding key via a special fitting on the arbor end.
    Hack watches, by comparison, usually had a setting
    mechanism associated with the winding stem. Again,
    according to my experience, chronometers were sent
    ashore for cleaning at reasonably frequent intervals
    and, at this time, were reset if the error had become
    unwieldy. They were also frequently rated while
    ashore, however, these shoreside rates seldom held up
    as sea.To allow a chronometer to run down was an
    unpardonable sin.
    The story of the US watchmaking industry, which had
    little experience in Chronometer manufacture, tooling
    up for such production at the onset of WWII is really
    remarkable, given the quality intruments produced.
    Good luck with the new toy.
    --- alex  wrote:
    > Dear list members,
    > I think that of all (archeo)-navigation topics,
    > chronometers were not
    > discussed
    > on this list in all detail.
    > I recently purchased one (a late Soviet one), and I
    > have many
    > questions.
    > 1. In the general books about chronometers (NOT the
    > navigation books)
    > they say that it is not important that a chronometer
    > shows "exact
    > time".
    > The important feature is the "constancy of rate".
    > For example, if a
    > chronometer
    > shows 24 hours and 1 second for each 24 hours
    > period, this is a good
    > chronometer,
    > 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
    > chronometer?
    > 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:-)
    > Alex.
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