François Auguste Claude

Background

Claude was born on December 30, 1858, in Strasbourg, France.

Education

Claude had no university degrees.

Career

Although Alsace had been annexed by Germany in 1871, Claude chose French citizenship as soon as he came of age; he immigrated to France and there served in the army. After being released from his military duties, he left his profession of industrial designer, at which he had worked for six years and went to the Bureau des Longitudes on his own initiative.

His entire career was spent at the observatory of the Bureau des Longitudes in the Parc de Montsouris in Paris: he became assistant calculator in 1884, chief calculator in 1898, assistant director in 1910, and director in 1929, which post he held until his death. Four times he was awarded a prize by the Academie des Sciences; nevertheless, since he held no university degrees, he was only an associate member of the Bureau des Longitudes (1906).

He devoted himself in a generous way to improving the techniques used in operations for which the Bureau des Longitudes had a responsibility: telephonic and radio-telegraphic transmissions of signals and observations of the passage and altitude of stars. His main contribution was the invention of the prismatic astrolabe (1899).

This instrument is made up of a horizontal telescope with an equilateral prism mounted in front of it. The light rays given off by a star reach the prism, in part directly and in part indirectly by reflection from a basin of mercury, thus providing two images to the telescope. These images coincide at the moment when the altitude of the star reaches 60. Observation of the passage of several stars allows one to determine the geographical coordinates of a certain place.

The first results, published in 1900, led the hydrographer L. Driencourt to collaborate with Claude in the perfection of this instrument and to adapt it to the needs of geodetic engineers. In 1938 A. Danjon built a high-precision instrument called the impersonal astrolabe on the same principle, and it has become one of today’s most important instruments of fundamental astronomy, facilitating the study of the earth’s movement around its center of gravity and the determination of the coordinates of fundamental stars.

Achievements

• Claude is best known as an astronomer, whose main contribution was the invention of the prismatic astrolabe in 1899.

Personality

Claude was a gracious and reserved man, who devoted himself in a generous way to improving the techniques used in operations.

References

• Dictionary of Scientific Biography Volume 3
  1971