The Institut de mecanique celeste et de calcul des ephemerides provides and publishes ephemerides of solar system bodies. It serves as the official and public source of ephemerides devoted to regulate calendars.

It performs theoretical research activities in the fields of celestial mechanics, planetology and mathematics. It initiates and coordinates observing campaigns of rare and specific celestial events.
 

In line with the Meridian of the Paris Observatory

1712-2012, three hundred years since Jean-Dominique Cassini, considered as the first director of the Paris Observatory, has died. On this occasion, the Observatory offers in his honor a special exhibition from May 9, 2012 until the end of the year. As part of this commemoration, IMCCE opens a site entirely and solely dedicated to one of the unknown wonders heritage of the Paris Observatory: the brass meridian line of the Cassini's great hall on the second floor of the Perrault building built between 1667 and 1671.

This line, drawn in the plane of the meridian of Paris, was built between 1729 and 1731 by Jacques Cassini II, son of Jean-Dominique Cassini. It was inspired by the canonical construction principles established by his father in 1655, when he built the meridian line of the Basilica of San Petronio in Bologna (Italy). More than a sundial, as we usually think, the meridian of the Observatory is a true high-precision astronomical instrument that JD Cassini also designated by the eloquent name of heliometer. It remains to date the only major existing meridian line - a length of nearly 32 m and provided with a gnomon located about 10 m above the floor of the hall, built within a not religious building.

Through this trilingual site (English, French, Italian), we suggest at once a historical journey in the eighteenth century, in the heart of the lights, and the discovery of an original and rare astronomical instrument, monumental and discreet, the meridian line, whose scientific posterity particularly note it was the first in which the slow decrease of the obliquity of the ecliptic - that is to say, the slight recovery (however temporary, as we now know that this movement is a slow oscillation with a very long period of 2.5° amplitude) in the space of the axis of rotation of the Earth - was demonstrated as an observable undeniable fact.

More about:
The website

The homepage of the Paris Observatory meridian website

 

Agenda 2012

For several years, the Observatoire de Paris and IMCCE publish this unique astronomical calendar.
Explore the sky until these distant galaxies, read about the scientific advances that have revealed the mysteries of the universe, find these men and women who have pushed the boundaries of knowledge! You will also find, this year, the latest advances in radio astronomy.

L'observatoire de la marine et du Bureau des longitudes au parc Montsouris 1875-1914

Why a marine observatory in Paris, in Parc Montsouris?

The answer is contained in this story, so far forgotten, that Guy Boistel has patiently reconstructed from the extensive archives of the Bureau des Longitudes, among others.

Caution : This Website was created with the Ministère de l'Education Nationale, the CNRS and the CNES support. Any use of the data published on this website requires the IMCCE agreement..