Setting the time on a chronometer - how?

[Kukri]

Basically Latitude has never been the problem .... the problem was Longitude and one of the main reasons the Chronometer was designed and put to use.

I'm intrigued by your statement ... because the age old professional Navigator would take a series of morning sun sights and then run them up based on speed / course on the plotting chart to ships noon. At local noon he would then obtain suns highest altitude - giving him Latitude. Simple course and speed correction to ships noon and draw the line intersecting with run-up morning sights ... giving the ships position at ships noon. Marc St Helaire of course. (I used Long by Chron as a cadet just to prove I could do it - but soon preferred MsH).
Because the ship had reports to make to owners / charterers via the Master - the noon position had to be available as near to noon as possible and not based on run back afternoon work.

Not trying to be smart - just commenting based on Commercial Shipping nav work.

I don’t think we are disagreeing at all. I was just pointing out the easiest route for a yachtsman beginner to gain confidence in using a sextant. I agree with your description of ship procedure.

 

[Kukri]

Oh, to set a chronometer:

A chronometer escapement is not self starting.

Turn it upside down in its gimbals. Set the time a minute or so ahead of actual GMT. Wind it. Turn it right way up again. Hold the mounting box in your hand. As the time approaches the time shown on the face, give the box a fairly quick half turn with your wrist. This will start the balance and it will now run. Wind it each day at the same time.

 

[lw395]

USED Symmetricom 15MHz Rubidium Oscillator atomic clock SA22C-0028C02D0002 | eBay

 

[zoidberg]

Bringing down the moon..... to its self-lit night horizon. More than a little tricky.

The best moon sight I ever managed was 40-odd miles out of La Coruna, grabbed in a hurry. Peering through the scope ( hadn't time to remove it ) along the moonlit silver path, there in the glittering field of view a pod of whales sounded one after t'other.... black silhouettes against the moonpath.

A sight I'll never forget.....

 

[Uricanejack]

Good luck finding an actual chronometer. At an affordable price. You will see them on eBay from ship breakers but these are almost always the modern quartz variety.
Any good quality watch or clock will do.

Traditionally the chronometer was kept in a lined box by the chart table with a thermometer and the temperature recorded with the daily rate.

Check the error daily and keep a record., today I usually check against GPS time. I have a nice Sony short wave Radio and can get WWV. On 5000 10000 15000 20000 25000. My radio is long out of production. I found one on eBay for a reasonable price. After my original died. I also have a Chinese knock off which was cheep and works.
A wire as an antenna is a big help. I managed to find a Sony wire antenna on line somewhere.
At one time I used BBC time signals. Which are still ok near the UK but most overseas broadcasts a relayed through satellite before retransmission now which includes a delay.

As said above. It’s the regular time check which ensures the accuracy.

 

[Kukri]

You don’t want an actual chronometer on a yacht. The motion is too violent and the detent escapement will jump and gain time.

What you want is either a navigational watch - often called a deck watch, although that term is now abused - or an American railroad watch.

In my picture in post 17 the two right hand watches are British deck watches from WW2, both actually made in Switzerland, an Ulysse Nardin and an EMT Tissot, the watch with the black face and the 24 hour dial is an American WW2 Hamilton 4992B air navigation watch from a B17 bomber and the one on a chain with vertical Arabic figures is a railroad watch. Any of these will keep time well enough to navigate a yacht. Hiscock used a railroad watch.

Be warned that, as you see, this can turn into a hobby...

 

[LadyInBed]

Do they still do the Shipping Forecast after as well ?

Yes

 

[Refueler]

Bringing down the moon..... to its self-lit night horizon. More than a little tricky.

The best moon sight I ever managed was 40-odd miles out of La Coruna, grabbed in a hurry. Peering through the scope ( hadn't time to remove it ) along the moonlit silver path, there in the glittering field of view a pod of whales sounded one after t'other.... black silhouettes against the moonpath.

A sight I'll never forget.....

Not recc'd 'bringing down the moon' ..... if the sky is relatively clear - better to do what is called ' Moonlight Stars ' .....

 

[vyv_cox]

As suggested it is not important to actually set the chrono to the right time but to check it against your choice of time signal and correct as required. And ( also as advised) best to be a good 10" ahead so that your corrections will always be negative.
We used the old rugby time signal for land based astro and tried to get the readings to 1/10th of a second.

Have sent you a PM. You may have missed it with the new format: it confused me.

 

[tudorsailor]

Thanks for all the replies. I points me to use my Suunto watch as a starter in my astro educational journey. I have synchronised it to Internet Time and 24 hours later it is still in sync. I doubt I will manage accuracy more than a second. so hopefully this will work for me.



All I need now is see the true horizon and to see the sun!

TudorSailor

 

[Refueler]

Any good quality watch or clock will do.

Todays watches and clocks have accuracy that was only a dream years ago.

Traditionally the chronometer was kept in a lined box by the chart table with a thermometer and the temperature recorded with the daily rate.

The Chart table usually had a recessed glass topped where the Chrono and its Error Logbook were kept.

Check the error daily and keep a record., today I usually check against GPS time. I have a nice Sony short wave Radio and can get WWV. On 5000 10000 15000 20000 25000. My radio is long out of production. I found one on eBay for a reasonable price. After my original died.

I still have my Sony ICF-7600D Multi-band radio .... the international version, not the clipped frequency European version.

As said above. It’s the regular time check which ensures the accuracy.

 

[AntarcticPilot]

If (a big IF!) you have network access, then this (The Official NIST US Time) is good - it uses NTP to correct for network delays, as should the clock on a PC. It used to state the error, but it was always less than a second. Any system using NTP ought to provide an accuracy better than a second.

 

[Kukri]

Most professionals count the seconds. This works best if you do it very regularly. If you have a spare person they can take note of the time when you say “on”. I don’t trust myself so I use a stopwatch.

 

[Norman_E]

This website is supposed to give accurate UTC. UTC - exact time now - Time.is

 

[Sandy]

1nm close inshore is very important ........... offshore is about as important as ???

Who relies on astronavigation within sight of land?

 

[Kukri]

Who relies on astronavigation within sight of land?

I knew someone who would routinely use a sun position line crossed with a shore position line or two if he couldn’t get enough good shore ones, because eg the coast was short of good charted landmarks. It’s not necessarily silly.

 

[Refueler]

Who relies on astronavigation within sight of land?

You misunderstand my comment ......

"1nm close inshore is very important ........... offshore is about as important as ??? "

Sun sights run up to noon to create a noon fix is subject to error that can be in miles .... star sights based fix is more accurate. But still subject to error and even in best will of the world - a mile or so out.

My point was 1nm error in position inshore can be disaster whatever means you use for position fix .... but 1nm offshore is not serious. I was not implying that anyone would do astro inshore ......

 

[emandvee44]

I have a Tamaya quartz chronometer on board. I check the time (error) monthly, using the GPS time and it is usually 0.0. or+0.5s on previous reading (it was set close to UTC last time the battery was changed about 3 years ago). It really is surplus to requirements as I can check my SEIKO sports watch against GPS time and use it to take sights.
Before you ask - the Walker log deck plates are not missing, they are installed on the boat

 

[tudorsailor]

If (a big IF!) you have network access, then this (The Official NIST US Time) is good - it uses NTP to correct for network delays, as should the clock on a PC. It used to state the error, but it was always less than a second. Any system using NTP ought to provide an accuracy better than a second.

On my laptop the NIST display is 1 1/2 - 2 seconds ahead of the time displayed on my phone using the app GPS time. However the NIST agrees with my radio controlled clock. I wonder what the explanation is for the GPS on the phone being different.

Meanwhile need to learn how to take a sight.......

TudorSailor

 

[AntarcticPilot]

On my laptop the NIST display is 1 1/2 - 2 seconds ahead of the time displayed on my phone using the app GPS time. However the NIST agrees with my radio controlled clock. I wonder what the explanation is for the GPS on the phone being different.

Meanwhile need to learn how to take a sight.......

TudorSailor

GPS time taken from a navigation sensor will normally be 1-2 seconds slow. This is to do with the update cycle of the system; the GPS time is intrinsically extremely accurate, but navigation systems display the most recent time received, not the current time. This is simplified and is not necessarily a precise description of the system, but the result is the same! NTS based systems take such latencies into account and offset them to give a more accurate time.