Started: nov 16, 2004
Last Update: july 7, 2005

A study for the Lunar map of Cassini.

Introduction

The table next to Louis XIV is covered with books and drawings. There is a architectural drawing of a fortification / stronghold, a drawing of a botanical? subject and a drawing of what at first glance appears to be a collection of light and dark smudges. A second and longer inspection suggested it to be a drawing of lunar features, more specific the area between Kepler, Oceanus Procellarum at the top and extending downwards to the region of Tycho (not visible).
A Lunar map was prepared by Cassini in the period 14 sept 1671 (Barthalot, 1982, p 48)- early 1679 and an engraving was presented to the members of the Académie on saturday, februari 18 1679 (i.e. during the weekly meeting of the Physics group) Le samedy 18.e de fevrier 1679. La Compagnie estant assembleé Mr Cassini a fait voir une grande figure dela Lune qu'il a fait graver et qu'on a examinée

Le samedy 18.e de fevrier 1679. La Compagnie estant assembleé Mr Cassini a fait voir une grande figure dela Lune qu'il a fait graver et qu'on a examinée

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Studies of the various phases of the moon were drawn in pencil by Sebastien LeClerc and from 1672 onwards by Jean Patigny (Weimer, 1979). In the Comptes des Batiments a payment is mentioned for 'dessigne taches de la lune' (drawing lunar spots) to Patigny in oct 1673. This might be related to a note for oct 18, 1673 on the 1788 lunar map in which a "Nouvelle grande Tache" is mentioned (Weimer, 1979, p 166; Launay, 2003, p 18).

Lunar map of Cassini 2nd edition: first edition 1679, engraved by Jean Patigny. Second edition 1787. 20 'Pouces de Paris' (54 cm) in diameter. This second edition is identical to the first, but for the text “Carte de la Lune ... de Jean Dominique Cassini”, engraved at the bottom.
Detail of lunar map of Cassini: the Kepler area. Nb the detail has been rotated 180 degrees compared with the original map image.

Cassini's Map in the 'Astronomical observations' of Donato Creti.

A series of eight small paintings by Donato Creti is on display in the Vatican Museum. Each of these paintings represents a rural scene in which a specific celestial body is observed. One of these paintings (see image on the left) shows two men observing the moon.
When I visited the museum in november 2004, I was struck by the way in which the moon was represented. I especially noticed the distinct cardioid shape in the Mare Serenitatis (see detail). This is almost certainly an artistic impression of the moon, based on the 1690 edition of Cassini's map (see below). Notice that the moon is shown as seen through an astronomical telescope, with the image up-side down.

Astronomical observations, 1711
Donato Creti, (Cremona 1671 - Bologna 1749)
oil on canvas, cm. 51 x 35 each panel
cat. 40432-40439
The series of Astronomical observations was commissioned in 1711 by the Bolognese count Luigi Marsili. He had the artist Donato Creti paint all the planets in as many small pictures and made a gift of these to the Pope to convince him of the importance for the Holy Church of an astronomical observatory. The gift made it possible to achieve his goal, because with the support of Clement XI (pontiff from 1700 to 1721) the first public astronomical observatory was opened in Bologna a short time later. The eight small canvases show the planetary system as it was then known: the Sun (cat.40432), the Moon (cat.40433), Mercury (cat.40434), Venus (cat.40435), Mars (cat.40436), Jupiter (cat.40437), Saturn (cat.40438) and a Comet (cat.40439). The planet Uranus, only discovered in 1781, is missing. The presence of the planets is dominant in the composition. They are depicted as observed with telescopes and various optical instruments (for which the artist had precise instructions) by small human figures in eighteenth century clothes, reabsorbed into the vastness of the nocturnal scene. source

Cassini's Lunar Map: a chronology

This chronology is based mainly on Launay (2003), with some additional information

date	event
1671, sept 14	Start of lunar studies by Cassini
1672, nov	Arrival of 34 feet Campani telescope
1679, febr 18	The '20 pouces' (=54cm) engraving is presented to the Académie des Sciences (Proces Verbaux). Several sources (Proctor, 1873, Pigatto & Zannini, 2001) give 1680 as the year of the engraving, which might stem from the information found on the 1788 edition. Weimer (1979) gives 18 avril, 1679, which seems an obvious error. Several sources also mention a map of 12 feet/ 3.60m that was constructed in this same period. (Proctor, 1873)
1690	A reduced map (lunar features are not labeled) is published in Nouvelles decouvertes dans le globe de Jupiter faites a l'Observatoire royal, Chez Jean Cusson
1692, june 30	A reduced map (lunar features are labeled with numbers and characters and a legenda of names around it) is published on a separate sheet, bound together with a memoir discussing in advance the lunar eclipse of july 28, 1692 (MARS X, 1730, page 129). Both the map and the text of the memoir contain the same list of lunar features which seems a bit redundant.
1711	Donato Creti paints a tableau that contains a lunar image, seemingly based on Cassini's lunar map of 1690
1787	A second edition of the '20 pouces' engraving is published
1788	A reduced map with an extensive historical note by Cassini IV is published, of which the text of the first paragraph is presented below (caution, this text was transcribed from an illustration in Launay 2003 and may (or better, probably will) contain errors): La plus grande Carte de la Lune qui est eté publieé est cette de vingt pouces de diametre que Domin.Cassini fit graver Vers 1680 d'après ses Observations pendant un intervalle de Neuf annees depuis 1671 jusqu'en 1679. les desseins Originaux de chaque Tache en particulier avec les dattes du jour, de l'heure, et toutes les autres circonstances de l'observation, écrites de la main de cet astronome se conservent soigneusement à l'observatoire Royal et forment un volume de soixante planches parfaitement dessinées de la main de le Clerc; et l'on croit que le celebre Mellan est l'auteur de la gravure de la grande Carte... Interesting as this note may seem, it appears to contain several errors (Weimer, 1979, p 167; Launay, 2003, p 16)