Horological Meandering

A chronometer shows the correct time at all times.  Imagine the following situation:

-          A watch gains 8 seconds during the day, but by leaving it dial-up overnight it is spot-on perfect in the morning, so over 24 hours it’s “perfect” ( “well within COSC limits”)

-          But over the 16 hours it was being worn it gained 8 seconds=+12s/d

-         Over the 8 hours it was dial-up it lost 8 seconds=-24s/d

-          For most of the day it’s not showing the right time.

Precision clocks in observatories didn't hack – they were left as undisturbed as humanly possible and the observatory maintained a log of accuracy using the timing of stars through a transit telescope as a reference.  Marine chronometers often didn't hack for the same reasons, and a log was kept of their accuracy.

You have to be able to read the time with the appropriate degree of precision for the usage.  Chronometers generally beat seconds.  In an observatory astronomers wanted an audible indication of seconds while they looked through the telescope for the exact moment of transit, and a one second tick was perfect for this.  When clocks started being kept in clock vaults an audible tick via electrical systems had to be created in the observing rooms  The dials of chronometers were designed to optimize the most important elements (seconds in an observatory clock).  

A chronometer has predictable errors or rate.  A chronometer was considered as a tool that would be left totally undisturbed and untouched until it’s accuracy became unpredictable (predictable errors can be taken into account).  Once errors became unpredictable it was cleaned, repaired, modified etc as appropriate.

The accuracy of a chronometer was judged in the long term (over a period of many months).

There was no mechanical-is-best snobbery - a chronometer was a tool, and the arrival of reliable electro-mechanical clocks was welcomed with open arms as it meant the clock could be kept deep underground in a clock vault with stable temperature and humidity and far removed from everyday shocks and vibrations, which added significantly to their long term precision, and the time oculd be displayed on electro-mechanical clocks via electrical signals.

Alex