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Accuracy of Harrison marine chronometer vs modern chronometer

Alouette

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Hello,
Harrison marine watch H5 is reported to lose one second in a month, see Longitude found - the story of Harrison's Clocks . I have measured the accuracy of a modern, digital clock which I bought at Decathlon, by comparing it with UTC online time servers, and it lost two seconds in a month.

I am flummoxed by the fact that a modern watch is less accurate that an old one. Do you have any comments on that?
 

musicguy

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I am flummoxed by the fact that a modern watch is less accurate that an old one. Do you have any comments on that?
This is why people are enthralled with these wonderful machines.


Rob
 

Tom McIntyre

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The performance of a clock for navigation depends on its rate, not the timekeeping. If a piece gains or loses a fixed amount in each period measured, it is a perfect navigational timekeeper.

Modern clocks checked against UTC are checked with civil time, which may involve location errors or other variables due to their common usage. That is just seculation on my part, but I suspect there is a local correction that is used by navigation systems dependent on the time signals.
 
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Dr. Jon

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The one second "accuracy" is bogus. The trip on the second trial, London to Barbados has a final error of 40 seconds, which was outstanding after a 6 week voyage, but it was disputed. As Tom wrote, it is rate but this is in dispute in Harrison's time. The Harrison team corrected for a known measured rate.

For navigation one nautical mile at the equator is 15 seconds of clock time. One half degree which was the prize allows 450 seconds.

Harrison chronometers cost about the same as a ship and they could make perhaps ten per year, although in fact only one was made by Kendal. Mudge has another idea for a marine timekeeper, not quite a complex as Harrisons, and about a dozen were ultimately made.

Detent chronometers required considerable development. Cooks voyage carried a lot which all failed leaving only Harrison's still running. Detent chronometers, ultimately replaced Harrison timekeepers but they were not in common usage until about 1850. They continued to improve as shown by published test records. The Hamilton model 21 instruments made in the early 1940's are some of the best produced. All cleared for navigation had a known rate and errors are departures from that rate.

The Marine Chronometer by Whitney has records for navigation chronometers from the 1960's. They did well enough for navigation but competition pocket and wrist watches did and do better.

Harrison did great work but it was expensive. A lot of improvement followed in technology and knowledge of how to use and rate these instruments. An important part of improvement is not only making timepieces more accurate but also less expensive. My high precision quartz wrist watch does better than 5 seconds per year.
 
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roughbarked

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Hello,
Harrison marine watch H5 is reported to lose one second in a month, see Longitude found - the story of Harrison's Clocks . I have measured the accuracy of a modern, digital clock which I bought at Decathlon, by comparing it with UTC online time servers, and it lost two seconds in a month.

I am flummoxed by the fact that a modern watch is less accurate that an old one. Do you have any comments on that?
Modern digital or analogue quartz clocks were always only accurate to + - 02 seconds per month.
They are cheap and nasty but as accurate as an accutron.
 

Alouette

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The performance of a clock for navigation depends on its rate, not the timekeeping. If a piece gains or loses a fixed amount in each period measured, it is a perfect navigational timekeeper.

Modern clocks checked against UTC are checked with civil time, which may involve location errors or other variables due to their common usage. That is just seculation on my part, but I suspect there is a local correction that is used by navigation systems dependent on the time signals.
I think that this answer is very unclear.
 

Alouette

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Je
The one second "accuracy" is bogus. The trip on the second trial, London to Barbados has a final error of 40 seconds, which was outstanding after a 6 week voyage, but it was disputed. As Tom wrote, it is rate but this is in dispute in Harrison's time. The Harrison team corrected for a known measured rate.

For navigation one nautical mile at the equator is 15 seconds of clock time. One half degree which was the prize allows 450 seconds.

Harrison chronometers cost about the same as a ship and they could make perhaps ten per year, although in fact only one was made by Kendal. Mudge has another idea for a marine timekeeper, not quite a complex as Harrisons, and about a dozen were ultimately made.

Detent chronometers required considerable development. Cooks voyage carried a lot which all failed leaving only Harrison's still running. Detent chronometers, ultimately replaced Harrison timekeepers but they were not in common usage until about 1850. They continued to improve as shown by published test records. The Hamilton model 21 instruments made in the early 1940's are some of the best produced. All cleared for navigation had a known rate and errors are departures from that rate.

The Marine Chronometer by Whitney has records for navigation chronometers from the 1960's. They did well enough for navigation but competition pocket and wrist watches did and do better.

Harrison did great work but it was expensive. A lot of improvement followed in technology and knowledge of how to use and rate these instruments. An important part of improvement is not only making timepieces more accurate but also less expensive. My high precision quartz wrist watch does better than 5 seconds per year.
Than you for this very nice answer. So the one-second claimed accuracy is obtained by taking the 40 second offset at the end of the voyage and correcting it for a know rate?

If I were able to do the same thing with my modern watch, I would obtain a post-correction accuracy which is better than 1 s per month?
 

Chris Radek

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If I were able to do the same thing with my modern watch, I would obtain a post-correction accuracy which is better than 1 s per month?
Perhaps! You should try it! I think if you are talking about a modern mass-market quartz, the main thing you will find gives you trouble is temperature changes, which was also one of the main problems in the old days.

If you use a wristwatch that you keep on your body, it might have a more consistent temperature than any ship's chronometer did...?
 

Dr. Jon

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No! The 40 seconds was AFTER correction. The rate was not zero. One nautical mile at the equator is 15 seconds of time. A look out on a tall ship can see out to about 10 nautical miles so they can make a land fall with with a time error of as much as 150 seconds, There are other errors so a better allowance is 100 or so seconds is more reasonable.

This was stunningly cutting edge in Harrison's time. The longitude prize was for 30 Nautical miles so Harrison crush it.

Portable timepieces capable of this accuracy were few and far between until the 1820's or so. By about 1800 many makers were doing better than Harrison and their timepieces cost a lot less.

I think the confusion relates to Harrison clock which was reputed to be within a second in a month. I am not aware that any of his clocks actually did this well but the Harrison Society is building or has built a clock that does this. I have a precision clock which the maker claims does 3 seconds per month. It will do this easily of I use the weight table to adjust it. In the 5 plus years I have run it has met this two or three times, without fine adjustment.

One second per month on a clock exposed to ambient air is amazing but by the late 1800's such clocks were doing a few seconds per year.

Harrison was aheead of his time but not by anything like 100 years.
 

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