Carte du Ciel

Carte du Ciel ("Map of the Sky") was an international project to map the positions of millions of stars — that is to say, of all stars to the 11th or 12th magnitude. In English, the project was sometimes known as the Astrographic Chart.

Related Topics:
Star - Magnitude

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It was begun in 1887 by Paris Observatory director Amédée Mouchez, who

Related Topics:
1887 - Paris Observatory - Amédée Mouchez

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realized the potential of the new technology of photography to revolutionize the process of making maps of the stars. He conceived of a project that would take 22,000 photographic plates of the entire sky, each 2°×2°, and enlisted the aid of numerous observatories around the world, who were each assigned a separate section of the sky to work on.

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The work involved two stages. In the first stage, astronomers determined precise positions of several thousand reference stars in various parts of the sky by timing their meridian transits. In the second stage, astronomers took photographic plates, and then the plates were turned over to a large number of semi-skilled female "computers" to determine the positions of the stars on each plate (before its modern meaning, the word "computer" meant a person who perform calculations). The "computers" would manually measure each star with respect to the dozen or so reference stars within that particular plate, and then perform calculations to determine the star's right ascension and declination.

Related Topics:
Right ascension - Declination

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