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> -----Original Message-----
> From: Navigation Mailing List on Behalf Of Jan Kalivoda

> The ship clock was regulated according to time sights of Sun and
> trusted between on sailing ships, at least if there wasn't any
> chronometer onboard. So the application of the Equation of Time
> wasn't important at sea without a chronometer, at least before
> 1833 (or 1832/34?), when GAT was superseded by GMT as the
> argument of the Nautical Almanac. This was caused by growing
> numbers of chronometers at sea, of course. Previously even the
> lunars were given in GAT.

Very helpful insights, Jan.  (And thank you for yours also, George).

Can anyone expand on the process that crews followed to keep their ship's
clock updated from time sights without a chronometer on board?  I understand
how the time sight, taken when the sun was nearly due east or west, gave
them an estimate of sun's LHA and therefore LAT.  And I understand how they
could compare that to their LAN estimate from their noon sun sight.  But how
did they convert the difference between LAN and LAT to a time for their
ship's clock?  Was it is as obvious as it seems to be -- simply adding the
number of hours and minutes of LAT to 1200, and then adjusting the hands of
the clock to match that time?

Slithery stuff indeed.

Jim

   

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