Carte du Ciel

The Carte du Ciel ( französ. sky map ) was a never finished international project to measure the positions of about one million stars to 11th magnitude, and to create a photographic map of the sky up to the 14th magnitude.

The project was conducted in 1887 by the Paris Observatory under its Director Ernest Mouchez in the way, who recognized the possibilities of photography for mapping the stars ( photographic astrometry ). He developed a project in which 22,000 photographic plates, each 2 ° × 2 ° size of the entire sky should be covered. He succeeded, with help from many observatories to win around the world, each of which is a part of the sky has been allocated for observation.

In a first stage exact positions of several thousand reference stars in different parts of the sky were determined by specific meridian circles with their declination and transit time through the meridian. After photographic images of the sky, the celestial coordinates ( right ascension and declination ) of many stars were recovered and determined laborious manual work and computation compared to the reference stars. But were semi-skilled workers, mostly women, employed in large numbers.


After decades of work, the project has been replaced by more modern techniques and never fully completed, although in 1958 a star catalog was published. The effort required was underestimated, so that the originally assumed period of 10-15 years was not observed.

Although some double stars and stars were discovered with high proper motion, the success remained low in comparison to the enormous time and effort. In addition, the astronomers were involved particularly in France engaged in a project that steady, little creative work required, while in other places the development of astronomy from the astrometry to astrophysics began.

Pictures of Carte du Ciel