[LEAPSECS] Marine chronometers, was Re: A new use for Pre-1972 UTC

[Joseph M Gwinn]

leapsecs-bounces at leapsecond.com wrote on 02/18/2009 09:56:10 AM:


> On Tue, 17 Feb 2009, Joseph M Gwinn wrote:

> >

> > > The navigators who used marine chonometers knew perfectly well that

> > > those chronometers did not keep the "right" time as measured by 

clocks

> > > on land being reset by telescopes.  Instead they knew that if their

> > > chronmeters were treated well they kept uniform time, and those

> > > navigators knew that getting the "right" time meant keeping a log of

> > > the difference between the "right" time of the clocks on land and

> > > their chronometer.

> >

> > They used the best cronometers then available.  Harrison's first 

attempt

> > at a chronometer was in 1730, and success came many years later, in 

1760

> > or so.

> 

> Steve is right. The key difference between H4 and Harrison's previous

> clocks is that he gave up trying to make a clock that keeps correct time

> and instead designed a clock that kept uniform time, which he could

> calibrate before a journey. This is often not well explained inthe 

potted

> histories.


I didn't trim enough when I quoted.  I was reacting to the complaint about 
navigation problems in 1707.  I think you're right about the history of 
Harrrison's clocks.  It wasn't until 1730 that Harrison achieved 
sufficient accuracy.

Joe