Carte du Ciel

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This article is about a star mapping project. For the astronomy software with a similar name, see Cartes du Ciel.

The Sydney 'Star Camera' used in the Carte du Ciel project, original publication, 1892http://www.powerhousemuseum.com/pdf/OPAC/40430.pdf

The Carte du Ciel (literally, 'Map of the Sky') and the Astrographic Catalogue (or Astrographic Chart) were two distinct but connected components of a massive international astronomical project, initiated in the late 19th century, to catalogue and map the positions of millions of stars as faint as 11th or 12th magnitude. Twenty observatories from around the world participated in exposing and measuring more than 22,000 (glass) photographic plates in an enormous observing programme extending over several decades. Despite, or because of, its vast scale, the project was only ever partially successful – the Carte du Ciel component was never completed, and for almost half a century the Astrographic Catalogue part was largely ignored. However, the appearance of the Hipparcos Catalogue in 1997 has led to an important development in the use of this historical plate material.

Participating observatories and stars measured in the context of the Astrographic Catalogue^[1]

Observatory	Declination		Epoch	No. of
(Zone)	From	To		stars
Greenwich	+90°	+65°	1892–1905	179,000
Vatican	+64°	+55°	1895–1922	256,000
Catania	+54°	+47°	1894–1932	163,000
Helsingfors	+46°	+40°	1892–1910	159,000
Potsdam	+39°	+32°	1893–1900	108,000
Hyderabad north	+39°	+36°	1928–1938	149,000
Uccle	+35°	+34°	1939–1950	117,000
Oxford 2	+33°	+32°	1930–1936	117,000
Oxford 1	+31°	+25°	1892–1910	277,000
Paris	+24°	+18°	1891–1927	253,000
Bordeaux	+17°	+11°	1893–1925	224,000
Toulouse	+10°	+05°	1893–1935	270,000
Algiers	+04°	−02°	1891–1911	200,000
San Fernando	−03°	−09°	1891–1917	225,000
Tacubaya	−10°	−16°	1900–1939	312,000
Hyderabad south	−17°	−23°	1914–1929	293,000
Córdoba	−24°	−31°	1909–1914	309,000
Perth	−32°	−37°	1902–1919	229,000
Perth/Edinburgh	−38°	−40°	1903–1914	139,000
Cape Town	−41°	−51°	1897–1912	540,000
Sydney	−52°	−64°	1892–1948	430,000
Melbourne	−65°	−90°	1892–1940	218,000

Contents

• 1Origins and goals
• 2The Astrographic Catalogue
• 3The Carte du Ciel
• 4Combination of the Astrographic Catalogue with Hipparcos
• 5References
• 6Other Links

Origins and goals[edit]

A vast and unprecedented international star-mapping project was initiated in 1887 by Paris Observatory director Amédée Mouchez, who realized the potential of the new dry plate photographic process to revolutionize the process of making maps of the stars. As a result of the Astrographic Congress of more than 50 astronomers held in Paris in April 1887, 20 observatories from around the world agreed to participate in the project, and two goals were established:

For the first, the Astrographic Catalogue, the entire sky was to be photographed to 11 mag to provide a reference catalogue of star positions that would fill the magnitude gap between those previously observed by transit and meridian circle instrument observations down to 8 mag – this would provide the positions of a reasonably dense network of star positions which could in turn be used as a reference system for the fainter survey component (the Carte du Ciel). Different observatories around the world were charged with surveying specific declination zones (see table). The Astrographic Catalogue plates, of typically 6 minutes exposure, were in due course photographed, measured, and published in their entirety. They yielded a catalogue of positions and magnitudes down to about 11.5 mag, and the programme was largely completed during the first quarter of the 20th century.

For the second goal, a second set of plates, with longer exposures but minimal overlap, was to photograph all stars to 14 mag. These plates were to be reproduced and distributed as a set of charts, the Carte du Ciel, in contrast to previous sky charts which had been constructed from the celestial coordinates of stars observed by transit instruments. Most of the Carte du Ciel plates used three exposures of 20 minutes duration, displaced to form an equilateral triangle with sides of 10 arcsec, making it easy to distinguish stars from plate flaws, and asteroids from stars.

A fascinating contemporary account of this vast international astronomical collaboration, published in 1912, is given by H.H. Turner, then Savilian Professor of Astronomy at Oxford University.^[2] Other aspects are covered in various papers in the Proceedings of IAU Symposium Number 133 held in 1988.^[3]