François Auguste Claude

Claude was born in Strasbourg and following the annexation of the Alsace region by Germany in 1871 he chose French citizenship and served in the army.

He then worked as a designer for six years and joined the Bureau des Longitudes at the Parc de Montsouris in Paris.

Despite having no formal university degrees, he became assistant calculator in 1884 and rose to the position of director in 1929.

His most important contribution was the design of a (60°) prismatic astrolabe which he published first in 1899 and then improved in collaboration with the hydrographer Joseph-Ferdinand-Ludovic Driencourt (1858-1940).

When a star reached a specific ascension angle above the horizon (60° in this case), its image and its reflection would be aligned in the viewfinder to obtain a precise angular measurement.