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 precisione and was quite expensive. The photographs could then be reproduced, either on thick paper or photographic paper.
However, not all the zones of the sky could be photographed for chart-making, or even if the plates had been made, they 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 pair 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 |
|
Recently the IAU Commission 8 working group on the AC and CdC plates, in its official web site has given a list of the deep CdC plates used for charting purposes whose paper charts got printed by the French company Schutzenberger until 1936. This list presents data which is partially in disagreement with the table by Couderc, i.e.:
- the charts for zone -52° to -59° were published by the Sydney Observatory;
- Heliogravures by Uccle cover only the zones +33°, +35°, +37°, +39°
- In addition, at the Palermo Observatory I have found some heliogravures for the zone +61°( Vatican) not mentioned in the table by Couderc, and heliogravures of the zone +11° from plates taken at Algiers and not Bordeaux.
It is thus important, in my opinion, that we know what has been published. But this type of material is not easy to catalogue, if one is not familiar with the information given in each chart.
The image on the right evidences the information which identifies each sheet :
For each declination (e.g. +1°, +2° etc.) there should be 180 charts, each taken at increasing right ascensions (from 0h 4m to 23h 56m, at intervals of 0h 8m), and numbered accordingly. Therefore, for each declination chart N. 1 derives always from a plate whose centre had 0h 4m AR, and chart N. 180 from a plate whose centre had 23h 56m AR. An easy way to catalogue the charts could be to use a model grid of 180 lines, in which to fill the cells with "date" and "printer" fields for the charts held. In order work out a global list of all the charts published, I have prepared a Work in Progress page which hopefully will be filled in with information send by colleague librarians who hold charts.
|
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The list of the sky charts held at the Palermo Observatory can be a starting point for the compilation of a global inventory of the charts published. If colleagues send me lists with their holdings to integrate my initial data, the resulting inventory can become a reliable reference source for present and future studies on the Carte du Ciel. Please contact donata@astropa.unipa.it
Donata Randazzo, 4 October 2006