Chronometer

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oldvarnish

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I've been reading the sextant thread. Astro navigation is, indeed, out of date but that doesn't stop it being interesting or satisfying, or prevent it from providing a considerable intellectual satisfaction when you 'get it right'.

So for those of us who still enjoy it, what are you using for a chronometer?
And in case anyone suggests using the GPS (which I have often done because I don't have a proper chronometer) it is worth looking at

http://leapsecond.com/java/gpsclock.htm

and seeing that GPS time and UTC are not the same thing.

(Not that many of my sights would notice the difference)
 
Interesting link, however when it says :

"GPS is now ahead of UTC by 15 seconds. "

I think you will find that this is the GPS internal clock, my GPS (Garmin) gives - on the screen - an accuracy of - / + 1 sec and I think this is probably true of the screens of all GPS's.

Could be wrong - I hope not !

:)
 
Navigational GPS is not optimized for time-keeping, and is often a second or so slow - not much, but enough to give a constant offset on fixes.

A bog standard quartz wristwatch will keep time accurate to better than a second a day; if it is routinely checked against time signals, then it is as accurate as you are ever likely to need. It is certainly far more accurate than a traditional chronometer. Once the watch has "settled down" it will also have a very constant rate, and if checked regularly, then I think a quartz watch treated LIKE a chronometer will be a very good time source. Of course, the price they are, you can carry a dozen!

Those who have access to the internet can use NNTP systems to get a time signal accurate to better than a second.
 
When I first started using astro in 1976, before the days of GPS, I used a quartz kitchen clock and checked its accuracy using the pips. These days I still use a domestic quartz clock - I keep one set to UTC for that purpose. I check it against the pips and the GPS time signal. The difference isn't enough to cause a problem for landfalls.

Easy trivia question - what part of the pips signifies the hour?
 
I used to have a Thomas Mercer, in its box, gimballed of course.
But mechanical chronometers have to be wound regularly to maintain an even rate. This is a nuisance of detail if you are not afloat 24 / 7.

Then one day I discovered how much these fetched at auction..:eek:

So I sold it and bought a Patek Phillipe Electronic from Kelvin Hughes which is correct to 1 - 3 seconds a year, and never looked back.
 
AntarcticPilot said:
A bog standard quartz wristwatch will keep time accurate to better than a second a day; if it is routinely checked against time signals, then it is as accurate as you are ever likely to need. It is certainly far more accurate than a traditional chronometer. Once the watch has "settled down" it will also have a very constant rate, and if checked regularly, then I think a quartz watch treated LIKE a chronometer will be a very good time source. Of course, the price they are, you can carry a dozen!
Click to expand...

You may find that a quartz watch kept on a wrist keeps better time than one treated like a chronometer. The crystal 'cut' used for watches has a noticeable temperature coefficient. Kept on the wrist, the body acts as a temperature regulator, but kept safe in its box the watch is exposed to ambient temperature changes.

One thing that has been noticeable in all the quartz watches that I've used is that they have all run slightly fast. I suspect that its so that the user will be early rather than late for appointments.
 
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