The photography campaign at the Paris Observatory

In his speech made to the Academy on August 1839, Francois Arago (1786-1853) expressed his admiration to Louis Daguerre’s process for fixing definitely the images on a support. In the same speech, Arago insist on the interest for the invention, which will allow more precise images, starting from the Moon. He also wrote a report on the subject.

Right from its birth, photography is associated to astronomy. This technique transforms radically selenography. During long hours of patient observations, tedious statements and laborious workload of graphic translation, brings new methods that needs new tools.

The first image of the Moon, which consisted of a daguerreotype, was taken by William Draper (1811-1882) in 1840, in the United States.  The image quality was somewhat low, and was for the moment not exploitable for a cartography enterprise. During the 1860s, Lewis Morris Rutherfurd (1816-1892) achieved significate results. His photographs are exploitable and already reveals a number of details of the Moon’s landscape with a strong finesse.

Thirty years later, on July 91894, Maurice Loewy, the director of the Paris Observatory and Pierre Puiseux (1855-1928) present an ambitious project to the Academy of sciences: the creation of a complete photographic atlas on the Moon.

During 500 nights of observations and about 6000 pictures taken, the Atlas photographique de la Lune is published at the national printing house, in 12 fascicles between 1896 and 1910. The shooting working conditions were often optimal and rare: the Moon needed to have a particular height, as a way to ensure that the photographs did not have any defaults linked to atmospheric perturbation. The wind could make the instruments unstable and lead to difficulties during shooting, the Moon’s movement needed to be followed with precision, in order to avoid any problems in clearness related to the laying time. The photosensitive solutions and the dipping process for the photographs needed to be often adapted.

In order to make this project in the best conditions, Maurice Loewy used the “grand équatorial coudé” from the Paris Observatory. The grand equatorial coudé is a revolutionary instrument inaugurated in 1891. It has a focal length of 18 meters, a photographic room with quality mirrors created by the Henry brothers. Additionally, it has a complex mechanism that permits to compensate the Earth’s movements.

The photographs on glass plates are enlarged, and then printed in a number of copies by using the rotogravure process. This process allows better images with greater quality of clearness.

With an enlargement of 2000, the atlas’s precision makes a good impression to the public at the Paris International Exposition in 1900. The craters’ details are admired by many, which were invisible until now, and the lunar landscapes is finally discovered; inaccessible for many centuries.

Puiseux’s and Loewy’s work will gain a durable success, until the era of the first space probe.