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Hi Alex,

Although these references do not contain technical
details on chronometer construction, you will find
more information in the various editions of Dutton's
Navigation texts. The later edition of 1985 broaches
the subject of Quartz Chronometers ... "capable of
maintaining an excellent rate, with the better models
having a deviation of less than 0.01 seconds from
their average daily rate that should not exceed 0.2
seconds per day. Many models have a sweep second hand
that can be advanced or retarded electronically in
increments of 1/10 or 1/100 second while the
chronometer is running." These instruments are battery
operated, thus obviating the need for winding. This
edition also broaches the use of atomic clocks for
ultra-accurate navigational systems and missile
guidance purposes, however, does not go into detail.
I have used the commercial models of the so-called
"atomic" clocks for sight purposes ashore and have
found them to be satisfactory, but have no personal
experience in their use at sea; I seem to recall
having read that these commercially available time
pieces are accurate to only withing 4-seconds,
however, am unable to quote a reference.

Older editions of Dutton, specifically that of 1934,
which was my initial navigation text, details the
older 20th century methods and procedures as followed
by the US Navy. At that time well run ships, with
presumably well heeled owners, carried at least two,
if not three chronometers, and there was advocated a
method of Chronometer comparison whereby the
regularity of of daily rate could be demonstrated -
using three chronometers it is possible to identify
the chronometer whose rate has changed, while with two
chronometers it is possible only to identify that the
rate has changed. This comparison procedure of course
presumes that a time signal is not regularly
available; it is a boring procedure which at one time
we had to learn.

There are other texts that include commentary on the
chronometer, Bowditch, Norie and Mixter being three
that come immediately to mind, however, none that go
into technical detail as to construction. To obtain
any detailed specifics as to construction one would
necessarily have to refer to watchmaking manuals, some
of which deal in great detail with the chronometer and
the methods of its manufacture.

To increase the accuracy of reading the 1/2 second
beat, I have sometimes used a 1/100 second reading
mechanical stop watch running simultaneously with and
synchronized with the chronometer second hand.

Regards,

Henry


--- Alexandre E Eremenko 
wrote:

>
>
> Henry,
> Thank you for your interesting information.
>
> > I suppose there might be some argument with
> respect to
> > methodology if the time between determination of
> > errors was particularly great,
>
> Strangely enough, I do not find any instructions on
> determining the chronometer rate in the navigation
> manuals that I have.
>
> I would imagine the following procedure (before the
> use of radio). While a ship is in a harbor, the
> correction
> would be determined daily by the time signals
> (gun shots, falling ball). From this the daily rate
> will
> be derived. And then used until the next harbor with
> time
> signals.
>
> > daily rate of 1.5 seconds losing. From a practical
>
> Very close to my chronometer: my one is loosing 1.37
> sec
> per day so far, and this is constant within a
> second.
>
> Here is a difficulty by the way: how do I determine
> the correction with say 1/2 second accuracy?
> The chronolmeter clicks and shows every 1/2 second.
> But my electronic watch (and Internet) clicks with
> only 1 second frequency, so errors of comparison are
> sometimes more than 1/2 second.
>
> > 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.
>
> That's a very good point!
> Now I know why my chronometer is 1.2 sec slow:-)
>
> By the way the factory certificate I have contains a
> lot
> of information from which I can infer how they were
> tested.
> I can post the details if there is interest.
>
> I cannot repeat this test because it involvs
> five 5-days periods
> running under given constant temperature:-)
>
> Alex.
>
>
>
>
>
>



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