Just what is a chronometer?
Since the beginning, humans have looked to the stars to find their way home. Rather poetically, it’s something we still do today, with satellites in our skies making up the Global Positioning System and beaming back our precise coordinates at the push of a button. However, long before we launched the navigational safety-blanket into the heavens, the best way to precisely traverse around our globe was by using an accurate timepiece – a chronometer – and the stars themselves.
A term that many believe was first coined by an English clockmaker by the name of Jeremy Thacker in the early 18thcentury, chronometers were highly accurate clocks. A few decades later this term would be applied to the marine chronometers aboard the naval fleets of the world’s oceans – vital (and precise) pieces of time-telling equipment that when used in conjunction with the position of the sun, moon, or known stars in the sky, could determine a ship’s longitude.
By the mid-19thcentury, accuracy was the name of the game in the watchmaking industry. And watchmakers and consumers alike, would seek to find only the most accurate watches. These watches would become known as chronometers and led to the establishment of yearly “chronometer competitions” at various astronomical observatories throughout Europe.
Pitting these highly-accurate watches against one another in a series of exacting trials, one of the most prominent locations for these watchmaking arenas was the Besançon Astronomical Observatory in France.
The watchmaking capital of France
First, a history of Besançon. Home to nearly 120,000 residents, the city of Besançon is located within the curves and twists of the Doubs river in eastern France. Not far from the Jura mountains, the ancient city is no more than a two-hour drive from the famed Swiss watchmaking regions of Saint-Imier and the Vallee de Joux. This proximity to the heartland of Swiss horology made it the perfect location for what would become the centre of the French watchmaking industry.
Coming to be not long after the French Revolution in the early 1800s, the industry quickly grew to employ tens of thousands of workers, and most if not all of the cities inhabitants today could speak for at least one member of their family tree as having made watches. In 1867 France’s famed watch manufacturer, LIP, opened their doors, remaining in operation for over one hundred years before the perils of the “Quartz Crisis” took its toll on the company and they were forced to cease production.
Yet horology remains a vital part of the cities identity, with several of the world’s largest watch brands opening service centres in and around the city. Brands like Breitling, Longines, and Audemars Piguet.
Perhaps two of the most impressive contributions that the city has made to the history of horology however are not watchmakers at all. The Cathédrale St. Jean de Besançon is home to a renowned astronomical clock – comprised of over 30,000 mechanical parts and several animated figures that re-enact Christ’s burial and resurrection every day. And then of course there is the Besançon Astronomical Observatory.
With amazing advances in optics being made, astronomy was beginning a new age of discovery in the mid-19thcentury. Astrologists were able to see the stars clearer than ever before and thus measure their movements across the sky with a newfound precision. What this also meant was that because the exact length of a second was then measured by the motion of the Earth around the Sun, observatories like the one in Besançon could accurately measure and set the time.
Inaugurated in 1885, the observatory quickly began providing chronometer certifications for watch brands. Shutting down in 1970 before reopening in 2002. Today the observatory certifies 100 watches a year – with a capacity to do up to 1000 – and their client list includes the likes of Laurent Ferrier, Kari Voutilainen, and AkriviA. Although nowadays, rather than compare a watches accuracy with movements in the sky, the observatory uses atomic clocks.
How they test
Pieces submitted to the Besançon observatory must all undergo the exact same stringent testing as all other chronometer rated watches – according to the ISO 3159 international standard. However, the French observatory requires one small (but not insignificant) difference – all movements must be cased and the watch presented in its final form.
The watches are then subjected to a battery of tests over a period of 16 consecutive days, with their accuracy tested in 5 different positions and 3 different temperatures, ranging from 8°C to 23°C and then finally 38°C.
If at the end of testing the average rate of time loss is within -4 to +6 seconds, the watch is certified with a certificate, individually numbered, and its movement stamped with the observatories legendary mark of the Viper.
Why it matters
Nowadays there are very few observatories left around the world that remain recognised to precisely measure and certify watches to chronometric standards. These “Keepers of time” have perfected the process of precision to an art form, with centuries-old techniques that have only been improved upon over time, culminating in the betterment of the entire watchmaking industry.
Besançon shares one of the richest stories of time, and to bear the Vipers head, is a sign of not only accuracy, but of horological history.
More photos below