Thread: Help with Surveying Chronometer

A very nice instrument. I have a couple of Mercer dial gauges. Mercer stuff was top shelf. I worked for a little while in a toolroom that had some 5" liquid filled Mercer dial gauges that read to 0.0001" and 0.001 mm. Kept in wooden fitted cases under lock and key in the tool store, only issued on the foreman's command.

Thanks for the comment Brian, I have a Mitutoyo vertical dial gauge PC linked if need be. Digital, reads down to 0.001 mm. Worth about $900 I belive with stand.

In surveying, Chronometers are (or perhaps more accurately were) used for timing astronomical observations with a theodolite, used for determining geographic north and latitude and longitude.

While I have not struck one with electrical contacts, these would have been to allow an external time reference, most likely to a chart recorder which also recorded the theodolite's readings, so that an observer could follow a star with the theodolite and get a whole series of readings to increase accuracy. This would perhaps have been used with a bubble sextant for air navigation, where a series of readings is necessary because of the unstable platform, although the standard bubble sextant has a clockwork averaging system.

The output could also have been used to control or time any activity needing an accurate time reference, such as a large telescope, or perhaps an earthquake seismograph station.

Both the time reference and the use of the chronometer itself have been replaced in the last forty years or so by broadcast time signals (e.g.WWV), and the use of celestial observation in surveying has been almost entirely replaced by satellite navigation systems over the last twenty years.

My guess is that the instrument is at least fifty years old, most likely of WW2 vintage.

John

Actually the electronic ones are not that expensive. My Star Tool Supply catalogue from New York shows the Mitutoyo models around the US$140 and Chinese and Indian equivalents US$80-110. The expensive ones are the clockwork models with jewel bearings. Mitutoyo top of the range US$470. Starrett digitals are quite expensive in the US$400-500 range. Starrett clockwork ones are expensive also, as are all Starrett precision tools nowadays.

My guess is that the instrument is at least fifty years old, most likely of WW2 vintage.

Who knows? It may have been used by Len Beadell for laying out Woomera, Maralinga, The Gunbarrel etc?







I can dream, can't I?

Originally Posted by JDNSW

In surveying, Chronometers are (or perhaps more accurately were) used for timing astronomical observations with a theodolite, used for determining geographic north and latitude and longitude.

My guess is that the instrument is at least fifty years old, most likely of WW2 vintage.

John

Pretty much hit it on the head, Astronony for Surveyors.

I used to use a chronometer like that when I was doing surveying at uni (mid 70s) although never did any astro work once I left uni. We used to use the time signal from VNG Lyndhurst to calibrate the chronometers.

I just happened to have a copy of Astronomy for Surveyors - J B Mackie 7th Ed (1971) on the bookshelf next to me and on page 127 is the setup for Astro work - Wild T2 theod, and a Mercer chronometer with electrical contacts plus plenty of other stuff.

The contacts on the chrono would make and break for 1/2 sec each for recording gear.

Could be worth a bit of money they were expensive when new - $800 - $1000 in the early 70s


Martyn