Chronometers and watches

[Adelie]

I would get 3 or more $10-11 waterproof Casio watches to be kept in the ammo box. I have also acquired a mechanical Molinja pocket watch from EBay for $35. It is currently in the ammo box with the backup GPS. I have not yet rated the the Molinja.

If accurate time is lost and needs to be reestablished without outside reference there are 2 methods descibed in “Self-contained celestial navigation with H.O. 208” by John S Letcher.

Of note regarding using ammo boxes as a Faraday cage, for the cage to work best contents need to be inside an insulator which in turn is inside the “cage”, a ZipLoc bag should do fine.

[Jim Cate]

And sometimes you get that calm evening with a perfect 3-star fix, and what a shame it would be to have dry hands, flat decks, and no idea by how many seconds your watch was off.

Ben,you are talking personal satisfaction, I was talking practical small boat navigation, especially referenced to back up usages when the primary method fails.

A good sextant and watch are surely nice to have, but simpler equipment (plastic sextant and cheap digital watch, roughly rated) have allowed me good landfalls. I later purchased a much better sextant and derived some pleasure from its use, but I didn't do all that much better in arriving at my destination.

Jim

[Orion Jim]

I have a Casio PRW 2500 which receives a time calibration radio signal daily and has a solar battery charger. Loads of functions and super accurate.

[Vasco]

Originally Posted by Jim Cate

But really, if taking sights from a low height of eye and from a pitching deck and with big enough seas to cause an obscure horizon, not having really accurate time is not a major error contributor. So, especially if only using celestial for a backup in the unlikely event of GPS failure, don't sweat a few seconds.



Jim

Very true. Especially to one who is not taking sights daily. Even with years of daily sight taking, hanging on in a small boat with any sea running, your observation error wll be much greater than any minor time error. If you do not have another crew member recording the time for you you'll need a stopwatch as counting and clambering down below will certainly increase your time error. Not to mention finding your glasses and refocusing your eyes. It gets worse with age. Your sight taking might get better with experience but the eyes always go. Of course with a noon sight (latitude only) you don't really need the time. Just hang in till the angle stops increasing.

[StuM]

Originally Posted by Orion Jim

I have a Casio PRW 2500 which receives a time calibration radio signal daily and has a solar battery charger. Loads of functions and super accurate.

Great as long as you are in within range of a time calibration service - in which case you are probably not in an area that calls for celestial navigation.


"Even when the watch is within range of a transmitter, signal reception may be impossible due to the effects of geographic contours, structures, weather, the time of year, the time of day, radio interference, etc. The signal becomes weaker at distances of approximately 500 kilometers, which means that the infl uence of the conditions listed above becomes even greater.• Signal reception may not be possible at the distances noted below during certain times of the year or day. Radio interference may also cause problems with reception.Mainfl ingen (Germany) or Anthorn (England) transmitters: 500 kilometers (310 miles) Fort Collins (United States) transmitter: 600 miles (1,000 kilometers) Fukushima or Fukuoka/Saga (Japan) transmitters: 500 kilometers (310 miles) Shangqiu (China) transmitter: 500 kilometers (310 miles)"

[grahamb]

...back in the day......Ondine ……...famous ocean racer...….had 3 chronometers...…...if one developed a fault......well you would not necessarily know...….if there 2 and one developed a fault well you would not know which one......so there were 3...….

[kantafig]

I have Pattek Philipe pocket watch for "chronometer", using £10 casio f-91w for taking sigts.

[ewsponberg]

Many thanks to all for your quick and detailed responses. I will copy these to a document and study your suggestions in more detail.

Eric

[barnakiel]

I use a plain Casio. About 10 usd apiece. I check this against gps time and take note of the extra seconds gained or lost. There is also ssb radio onboard (which I do not use for time signals.)

I wish I had a proper mechanical chrono but these are way beyond my economy AD 2019.


$$$ pieces of jewellery.


b.

[Adelie]

Originally Posted by barnakiel

I use a plain Casio. About 10 usd apiece. I check this against gps time and take note of the extra seconds gained or lost. There is also ssb radio onboard (which I do not use for time signals.)

I wish I had a proper mechanical chrono but these are way beyond my economy AD 2019.


$$$ pieces of jewellery.


b.

If you search Ebay for Molinja Pocket Watch you get those plus a lot of similars for $25-60 working. Have no opinion as to whether error rate will be constant.

[barnakiel]

Originally Posted by Adelie

If you search Ebay for Molinja Pocket Watch you get those plus a lot of similars for $25-60 working. Have no opinion as to whether error rate will be constant.

yep.


These and Pobedas look good value.


I also like the Glasshute sets that buy you a small gimbaled chrono in a box and a wristwatch in one price. Just the price is ehhhhhhhhhh... ;-)


Economy-wise some omegas seem good buy, as these can be sold later with not that much loss of money.


I was also thinking of buying a gold one - so that over time the price of the mineral would probably let me sell the watch at no $ loss at all.



barnakiel

[SeanPatrick]

You can also just shoot a lunar to get UT and correct your timepiece from that. Or just use a stopwatch and start it at the time you shoot the lunar, then note how much time has passed when you take each sight and add that to the UT you got from the lunar. Of course, you can't shoot a lunar any time you want to - but (aside from the time very near a new moon) there is usually an opportunity for one at some point every day/night. (Barring cloud cover, of course.)

And don't let anyone tell you that lunars are difficult and/or time consuming. They can be done in a matter of a few minutes with a scientific calculator or - if you want to go the completely non-electronic route - a set of tables like Stark's. If you're able to wrap your head around sight reduction, you can do lunars. And if anyone here needs help learning how it's done, I'd be happy to assist.

[CassidyNZ]

Originally Posted by kantafig

I have Pattek Philipe pocket watch for "chronometer", using £10 casio f-91w for taking sigts.

You probably mean a Patek Philippe?

[ewsponberg]

To all, I am finally reporting on what I have been able to do regarding chronometers and watches. Sorry for the delay--we have had a lot of Australia to see. I followed the advice of those above that said to get 3 cheap watches of a good brand, and Casio figured prominently in the brands mentioned. We searched all over metropolitan Australia for Casio or Timex watches, both of which we have had before. The Casio in analog form were non-existent; only digital were available in some places. And no one in Australia seemed to carry Timex watches of any kind. All the other well-known brands like Seiko, Bulova, and the other fashion brands were just too expensive, generally $150 to $1,000 and higher.

So, relying on good ol' Amazon, I was able to find inexpensive Casio analog watches for OZ$24.41 each, about US$17.00. The watch model number is MQ-24-7BLL, a men's watch with white dial, no date window, and a black plastic strap. Interestingly, these watches were shipped to us here in Bundaberg, Queensland, from St. Peter Port, Guernsey, in the UK Channel Islands (half a world away) and shipping was free!

I have set the time on each to UCT and they are within a second of each other and within a second of UCT. I've mounted them on a paper towel cardboard tube, labeled them A, B, and C, and am keeping track of their accuracy. So far, so good. See the photo.

So I wish to thank all of your for your input. It all seemed good advice.

Cheers,

Eric

[Paul L]

You might want to record ambient temperature during the period, as that will have a large effect on the error. That is why wearing a digital watch ( ei5th or without a digital didplay) can help keep it accurate, as the temperature changes little due to body heat.