Foucault's Marseille reflector
bâztâbgar-e Foucault-ye Marseille
Fr.: réflecteur marseillais de Foucault
The first functioning → reflecting telescope with a silvered glass mirror. It was built by Léon Foucault in 1826 for the Marseille Observatory. The mirror of 80-cm in diameter (f/d = 5) had an excellent quality. The telescope was used for a century as a visual instrument. Edouard Stéphan (1837-1923) used it from 1871 to 1884 to find 800 high-brightness galaxies, among which the → Stephan's Quintet. From 1906 to 1962 the telescope was used by Robert Jonckheere (1888-1927) to discover 3,350 new binary stars. In 1873, following an idea of Hippolyte Fizeau (1819-1896), Stéphan attempted to use it as an → interferometer to measure the diameter of a number of stars. In 1914 Charles Fabry (1867-1945) and Henri Buisson (1873-1944) used the telescope to obtain the first astronomical Fabry-Pérot interferogram, on the → Orion Nebula.
After the French physicist and optician Léon Foucault (1819-1868); Marseille (Observatory), the second largest city of France, located on the south east coast of the Mediterranean Sea, from L. Massalia, from Gk. Massalia; → reflector.