Marine chronometers

[David Bridgen]

Reference is often made to the accuracy of marine chronometers, and I have no doubt that this was once very important.

However, during my sea time in the late 50s and the 60s, I was led to believe that absolute accuracy, while perhaps desirable, was less important than a known constant error rate. At that time, one of the R.O's duties was to receive daily time signals, often from the B .B.C., such that the duty deck officer could check the timepiece and log its error. The absence of a reliable time signal for a few days then becoming nothing to get excited about.

I suppose today that technology has long ago resolved many, if not most, uncertainties.

But I would like deck officers, both ancient and modern, to comment on what I was told all those years ago.

[j.sabourn]

Chronometers... you are correct in what you say of the past. Is not even called GMT now is Universal Standard Time if it hasny been changed again. In days of yore the chron. would go I beleive for 2 days, However was wound each day at the same time so as to use the same part of the spring. Used to be a standard fine of a case of beer for any second mate who allowed the chronometer to stop.Every chron. I sailed with had an error it may have gained a second or lost a second a day but as long as one knew was no problem. Nowadays with atomic clocks or whatever they call them and GPS systems, they are probably looked on as antiques. Many a master carried his own Chronometer up until about the early 50"s. You couldnt find your Longitude without it. Regards John S.

[Don Rafferty]

I suppose today that technology has long ago resolved many, if not most, uncertainties.
.

Time - no less relevant today than a few decades ago that most of us remember, or even two or three centuries.

Modern GPS relies on the time difference between a sent and received signal to a satellite to establish a position on earth accurate to at least a metre, and sometimes a lot less - we still need time, we just use it differently.

[j.sabourn]

Ivan.. When did they start putting sextants on ships. The only one I ever had was an ex Navy one from the Naval Stores which got sold off at 10 pounds each, they were of course Verniers. Think the shipowner started putting a ships sextant on board when crews were being flown out to join and leave ships to save on the luggage allowance, the same with all the heavy gear seaboots oilskins etc. dont think he did it out of the goodness of his heart, so imagine would have been in the mid 60". Sold my sextant as an antique, would be worth a lot more today. Cheers JS

[j.sabourn]

#3... Just waiting for them to invent a time machine and we can all go back to the past. When you talk about measuring distances with time as per GPS you are in the realms of a totally different version of Navigation. Celestial Navigation is based on trigometric values of heaveny bodies, which have been there since time began or almost so, GPS is based on man made objects floating around in orbit around the earth, and in any full scale conflict would more than likely cease to exist for the use of ship positioning. Nelson used the same navigation techniques as we did up until the 70"s. Cheers JS

[j.sabourn]

Ship Positioning.... Anyone who has sailed on survey vessels such as seismic, will know that they carry navigators. These are not navigators as we know them. The ones I spoke to afloat I had my doubts whether they ever used Lat. and Long as a means of positioning. They had their own terms of ref. and Lat and Long did not come into it. They had vectors and different lines going in all directions and worked of a GPS system. Anyone thinking of a Navigator working for an oil company re survey should not think of him as a normal ships navigator.Cheers JS

[Ivan Cloherty]

Ivan.. When did they start putting sextants on ships. The only one I ever had was an ex Navy one from the Naval Stores which got sold off at 10 pounds each, they were of course Verniers. Think the shipowner started putting a ships sextant on board when crews were being flown out to join and leave ships to save on the luggage allowance, the same with all the heavy gear seaboots oilskins etc. dont think he did it out of the goodness of his heart, so imagine would have been in the mid 60". Sold my sextant as an antique, would be worth a lot more today. Cheers JS

Don't know John, like all others I knew, always carried my own, never let anyone use it, except cadets under supervision, I think everyone took real care of their own, because lending it to someone meant readjusting the mirrors everytime, something you always never had time to do when awaiting that elusive glimpse of the sun or star in inclement weather. Always checked mine before putting it away. Never sailed on a ship with a company sextant, but presume like you, that they started to appear on board when crews started to join ships by air. I know that we were not supplying them on UK ships in the 60/70's when Supt for a British Company, but when working for the Swiss and Arabs in 70/80's they were supplied by the company, but some of the Masters and mates carried their own even then, never trusting the abused company one.

[Don Rafferty]

I know that apart from winding it and noting the error, nothing was done to the chronometer aboard ship and was sent ashore for adjustment, but what was time when that happened, when did the error become too great?

[j.sabourn]

Probably when the daily error wasnt constant or nearly constant, and one couldnt rely on appling the calculated error as changed daily. As sunsights were about 0800/0900 a morning Time Check was advisory. Usually in the early hours of the morning just before daybreak when the mate was taking his star sights the R/O would probably be in his pit. and would probably be over 12 hours since the last time check. If error was constant was no problem as said, when the error was erratic was time to get sent ashore to Lilley and Gillies or whoever Cheers John S

[Captain Kong]

I still have two chronometers off ships that I took to the scrap yards. Not saying what ships cos the company may want them back.
I believe the best sextants were the German Plath. I used them occaisionally when the owner allowed me to but usually it was the ship`s own sextant. Esso alway provided them.
Cheers
Brian.