Foucault Reflecting Telescope

Foucault Reflecting Telescope

C026/4885 Rights Managed

Request low-res file

530 pixels on longest edge, unwatermarked

Request/Download high-res file

Uncompressed file size: 50.6MB

Downloadable file size: 4.9MB

Price image Pricing

Please login to use the price calculator


Caption: The 80cm reflecting astronomical telescope of Leon Foucault (1819-1868), the French physicist, was built in 1862 in Paris and was moved to the Marseilles Observatory in 1864. Here it remained in service until 1962, giving it a working life of 100 years. This instrument has been called the first modern reflecting telescope due to the advances Foucault had made in the manufacture and testing of telescope mirrors. Previously, mirrors had been made from speculum, a copper and tin alloy but they were optically limited. Foucault found that glass was easier to work and had a better surface finish which, by depositing an ultra-thin layer of silver on the front surface, Foucault was able to produce an optical-quality, first-surface parabolic mirror, far superior to speculum mirrors. Equally important was his “knife-edge” test to measure the shape of telescope mirrors.

Release details: Model release not required. Property release not required.

Keywords: 19th c, alloy, astronomical, astronomy, deposition, equatorial mount, foucault, french, knife-edge test, marseilles, mirror, optical, parabolic, physicist, reflecting telescope, silver, speculum, telescope

Licence fees: A licence fee will be charged for any media (low or high resolution) used in your project.