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Daniel Crouch Rare Books

Carte de la Lune.

Cassini’s seminal Lunar Map

557 by 567mm. (22 by 22.25 inches).


Cassini made approximately sixty drawings of the moon between 1671 and 1679, with the assistance of the artists Sebastien Leclerc and Jean Patigny. The observations took place when possible during lunar eclipses, which provided unusual light patterns and a clearer view of the surface. Fifty-seven of these drawings remain in the library of the Paris Observatory. The copperplate for the map, engraved by Claude Mellan, was created with the help of the drawings. Both the technology and the observations made were so exciting that a manuscript map of lunar features appears in a 1680 painting at Versailles by Henri Testelin, showing Colbert introducing members of the Academy of Sciences to Louis XIV. 

The three-dimensional quality given to the lunar features by Patigny and Mellan remained unsurpassed until the advent of photography. It was the first accurate map of the moon, completely “overshadowing” the contributions of Cassini’s predecessors, which were highly stylised and lacked interior detail. Contemporary observers commented on their simplicity: Robert Hooke compared the portrayal of the lunar formation Hipparchus by Johannes Johannes Hevelius and Cassini’s teacher Riccioli to show the relative paucity of information they provided.

Cassini’s map, however, shows a level of detail visible only through a telescope of twenty feet in length or longer. The dimensions and positions of the major features are reasonably accurate, but the map’s real strength lies in the wealth of verifiable information given on the lunar limb. The moon is oriented to the south, but with the lunar axis rotated about 30-45 degrees clockwise.

As well as representing a scientific advance, Cassini’s map also staked a claim in a religious dispute. The moon had long been associated with the Virgin Mary, and an analogy drawn between the supposed purity of its surface and her chastity. Observations of the moon from Galileo onwards, however, had shown that the moon’s surface was in fact far from perfect. It was covered with mountain ranges and pitted with craters. Cassini’s map was another firm rebuttal of the theory of the immaculate moon: despite this, Catholic astronomers only gave up the concept at the end of the seventeenth century.

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