The Besançon Astronomical Observatory () is an astronomical

observatory An observatory is a location used for observing terrestrial, marine, or celestial events. Astronomy, climatology/meteorology, geophysics, oceanography and volcanology are examples of disciplines for which observatories have been constructed. Th ...

owned and operated by the

Centre national de la recherche scientifique The French National Centre for Scientific Research (, , CNRS) is the French state research organisation and is the largest fundamental science agency in Europe. In 2016, it employed 31,637 staff, including 11,137 tenured researchers, 13,415 eng ...

(CNRS, National Center for Scientific Research). It is located in

Besançon Besançon (, ; , ; archaic ; ) is the capital of the Departments of France, department of Doubs in the region of Bourgogne-Franche-Comté. The city is located in Eastern France, close to the Jura Mountains and the border with Switzerland. Capi ...

, France. In the past, the Besançon Observatory participated in assessing and rating Swiss timepiece movements for accuracy. As marine navigation adopted the usage of mechanical timepieces for navigational aid, the accuracy of such timepieces became more critical. From this need developed an accuracy testing regime involving various astronomical observatories. In

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

, the Neuchatel Observatory, Geneva Observatory, Besançon Observatory and

Kew Observatory The King's Observatory (called for many years the Kew Observatory) is a Grade I listed building in Richmond, London. Now a private dwelling, it formerly housed an astronomical observatory, astronomical and Terrestrial magnetism, terrestrial mag ...

were examples of prominent observatories that tested timepiece movements for accuracy. The testing process lasted for many days, typically 45 days. Each movement was tested in 5 positions and 2 temperatures, in 10 series of 4 or 5 days each. The tolerances for error were much finer than any other standard, including the ISO 3159 chronometer standard that other testing bodies such as

COSC The Contrôle officiel suisse des Chronomètres (COSC), the Official Swiss Chronometer Testing Institute, is the institute responsible for certifying the accuracy and precision of Swiss watches. Background Founded in its current form in 1973, t ...

use. Movements that passed the stringent tests were issued a certification from the observatory called a Bulletin de Marche, signed by the Director of the Observatory. The General Bulletin Order stated the testing criteria, and the actual performance of the movement. A movement with a bulletin from an observatory became known as an Observatory Chronometer, and such were issued a chronometer reference number by the Observatory. The role of the observatories in assessing the accuracy of mechanical timepieces was instrumental in driving the mechanical watchmaking industry toward higher and higher levels of accuracy. As a result, today high quality mechanical watch movements have an extremely high degree of accuracy. However, no mechanical movement could ultimately compare to the accuracy of the quartz movements being developed. Accordingly, such chronometer certification ceased in the late 1960s and early 1970s with the advent of the quartz watch movement.

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Publications of Besançon Observatory
digitalized on

Paris Observatory The Paris Observatory (, ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world. Its historic building is on the Left Ban ...

digital library {{DEFAULTSORT:Besancon Astronomical Observatory Astronomical observatories in France Buildings and structures in Besançon Education in Besançon

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