Talk:Marine chronometer

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WikiProject Time assessment rating comment
Basically a B-class. Certainly High importance, due to its intrinsic contribution to precision longitude calculation.

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—Yamara ✉  16:42, 7 May 2008 (UTC)

Definition and chronometers today
The phrase under Today is inadequate for this article:

"GPS, and atomic clocks, have made mechanical clock-chronometers obsolete."

This is probably true for mechanical watches and chronometers, but it is certainly not true for digital chronometers. As one web site points out, "Murphy's Law was invented on a small boat at sea." GPS units can be lost or fail to work. Signals can be lost. They can also be blocked, or the satellites or transmitters destroyed, in a conflict. The U.S. Coast Guard still requires the knowledge of sextant use for its examination. A precise and accurate chronometer is still needed at sea today.

That leads to the definition in the article of a marine chronometer being mechanical. It need not be. It simply needs to be the most accurate, autonomous clock available for use at sea. --Parsa 01:49, 23 September 2007 (UTC)

Mechanical chronometers confusing
The section on escapements, escape wheels, etc is confusing. Could it be rephrased into simpler terms, or could the terms used be defined for the lay public? --Badger151 (talk) 03:38, 26 September 2008 (UTC)

Factual error in usage description in history section
"Since the Earth rotates 360 degrees every day (that is, 24 hours or 1,440 minutes)" This is just not true. As described in 'Earth's rotation', the earth rotates 360 degrees in 23:56:04 (stellar day). I have tried to improve it by adding 'with respect to the sun' but I think even that isn't strictly true. Isn't there an equation of time correction? Can anybody come up with a concise but accurate description 69.110.223.12 (talk) 04:48, 16 February 2009 (UTC)


 * I've modified your phrase to the more correct term ficticious mean sun, although that is obvious jargon which may need further explanation. An alternative would be reword the section to avoid mentioning the kind of Sun. — Joe Kress (talk) 06:47, 16 February 2009 (UTC)


 * I've removed both your changes, since 360° is 360° regardless of any reference point.


 * You are correct that the rotation is in a siderial day and not a solar day. However, the equation of time is irrelevant - it only applies to correcting the apparent solar noon to mean solar noon.--Michael Daly (talk) 06:58, 16 February 2009 (UTC)

Necessary and sufficient?
Redundant? — Preceding unsigned comment added by 68.126.178.74 (talk) 09:11, 5 June 2011 (UTC)


 * Necessary and sufficient is not redundant. For some result something may be necessary, but that may not be the only thing required to obtain that result. On the other hand, necessary and sufficient means that something is necessary and nothing else is needed to obtain the result. — Joe Kress (talk) 01:57, 6 June 2011 (UTC)

Accuracy of quarz clocks
The deviation of a normale quarz clock / watch is up to 30 seconds per month, not per year. Example: Casio states in its manuals that the accuracy is + / - 30s per month. Thats for watches priced around 40 € - 200 €. --88.153.183.57 (talk) 00:13, 16 February 2012 (UTC)


 * The reference cited in the article lists many watches with seconds per year accuracy, most costing hundreds or thousands of Euros. According to ordinary quartz watches have a typical accuracy of 15 seconds per month, but thermocompensated quartz watches have a typical accuracy that is better than 15 seconds per year. — Joe Kress (talk) 00:02, 19 February 2012 (UTC)

Electronic marine chronometer
When reading the article you get the impression that technology jumped from mechanical chronometers to GPS more or less instantly. That is of course not quite true. While many purely mechanical chronometers where still in regular use until GPS era they where not the only ones. In the 60s electronic quartz marine chronometers became available with advantages over purely mechanical counterparts. Many of them even back then where capable of a precision within 10 seconds pr. year or even less. The advantages of the electronic quartz models is not only the greater overall precision but they're also less temperature sensitive which means that when calculating offset it'll be closer to reality then if using a mechanical - the rate is more stable than a mechanical. Add to that more rugged and they don't need winding - just battery replacing once in a while (once a year typical in order to continue running but can vary from model to model). Those electronic ones were the most common ones in the 70s and well into the GPS era as backup system before being replaced for a more integrated solution (on especially larger vessels). There were also made tuning fork marine chronometers but to my knowledge they didn't play a major part in history as they where neither the first electronic ones or the most precise. — Tilt u (talk) 11:42, 4 January 2013 (UTC)

First use of the word "Chronometer" in 1713 by William Derham rather than in 1714 by Jeremy Thacker?
It is suggested by Katy Barrett/Eoin Phillips that the word Chronometer was "First used by the clockmaker William Derham in 1713, the word was picked up by other projectors, notably the potential Scriblerian scam Jeremy Thacker" see their essay on the Chronometer here: http://cudl.lib.cam.ac.uk/view/ES-LON-00003/1. Irisbox (talk) 15:01, 23 July 2013 (UTC)

A user's pragmatic definition of a marine chronometer.
For a few years I was a Radio Officer in the British Merchant Navy. One of my daily duties was to tune in to a source of time signals, perhaps WWV or the B.B.C., and the duty Deck Officer would record the ship's chronometer error. I was told that the absolute accuracy of the Chronometer was much less important than a daily record of its error. In the absence of a time signal for a few days, not unusual in the Pacific where reception was frequently poor due to static, the error was interpolated from the chronometer's log. It was a predictable error which was held in high esteem.

Syncopator (talk) 18:22, 26 July 2013 (UTC)

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Has an incorrect claim
It claims..." Timepieces made in Switzerland may display the word 'chronometer' only if certified by the COSC (Official Swiss Chronometer Testing Institute).", this is not correct. Certified Marine Chronometer watches have been made in Switzerland that have the word Chronometer on them, but they are not certified by COSC, but by a different agency in France. — Preceding unsigned comment added by 208.118.28.7 (talk) 13:13, 22 January 2016 (UTC)

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