The Carte du Ciel enterprise

The sky charts

In order to produce the sky charts, the photographic plates for the Carte du Ciel had to be transformed into engraved copper plates - a process which required a high degree of precision and was quite expensive - and then be printed on thick paper. Alternatively, the plates could be reproduced directly on photographic paper.

However, not all the zones of the sky could be photographed for chart-making, or even if the plates had been exposed, charts were not printed.

At the IAU 14th General Assembly, held in Brighton, UK, in 1970, the President of Commission 23 in charge of the enterprise, Paul Coderc (Paris Observatory) declared the Carte du Ciel an "unachieved project" and presented the following table which described its current status

Sky zone	assigned to	carried out by	Sky charts

+90° to +65°	Greenwich		All charts printed
+64° to +55°	Vatican		Heliogravures for 1/3 of +55°, +56°, +57°; the remaining printed on photographic paper
+54° to +47°	Catania		NONE
+46° to +40°	Helsingfors		NONE
+39° to +32°	Potsdam	Uccle	Heliogravures for the entire zone printed and distributed by Uccle
+31° to +25°	Oxford		NONE
+24° to +18°	Paris		Heliogravures for the even zones +18°, +20°, + 22°, +24°
+17° to +11°	Bordeaux		Heliogravures for the even zones +12°, +14°, +16°
+11° to +05°	Toulouse		Heliogravures for the odd zones +5°, +7°, +9°
+04° to -02°	Algiers		Heliogravures for the odd zones -1°,+1 °,+3°
-03° to -09°	San Fernando		Heliogravures for the odd zones -5°, -7 °,-9°
-10° to -16°	Tacubaya		Heliogravures for the zones -11°, -13 °, -15°, -16 °
-17° to -23°	Santiago	Hyderabad	NONE
-24° to -32°	La Plata	Cordoba	Heliogravures for the zone -25° only
-33° to -40°	Rio de Janeiro	Perth	NONE
-41° to -51°	Cape of Good Hope		NONE
-52° to -64°	Sydney		NONE
-65° to -90°	Melbourne		NONE

On the whole, the information given in the table seems to match the lists of printed charts held at the Palermo Library, with some exceptions:

- Heliogravures by Uccle seem to cover only the zones +33°, +35°, +37°, +39°

- Some heliogravures for the zone +61°( Vatican) do exist

- Heliogravures for the zone +11° derive from plates taken at Algiers and not Bordeaux.

The image on the right evidences the information which identifies each sheet :

Declination (e.g. Zone -1°)
Chart number (N° 179)
Observatory which issued the chart (Observatoire d'Alger)
Date when the plate was taken (27 Octobre 1911)
Name of the observer who exposed the plate (Mr. Renaux)
Name of the printer (L. Schutzenberger)

Charts for each declination (e.g. +1°, +2° etc.) are taken at increasing right ascensions, and numbered accordingly. The varying lenght of the interval determines the total number of plates for each declination.

E.g.: For intervals of 8 minutes, charts are 180 (from n. 1, derived from a plate having centre at 0h 4m AR, to n. 180, from a plate centered 23h 56 m AR); for intervals of 12 minutes, charts are 120. For intervals of 10 minutes, charts are 144.

Links to sky zones in the table, lead to information on the work made at some of the Observatories involved with Carte du Ciel and to the lists of charts held at the Palermo Observatory Library.

Donatella Randazzo, 6 November 2012