Prismatic telescope or micrometer by Rochon, signed "Herbage - Lot 25

Lot n° 25
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Result : 3 800EUR
Prismatic telescope or micrometer by Rochon, signed "Herbage - Lot 25
Prismatic telescope or micrometer by Rochon, signed "Herbage opticien Quai de l'Horloge du Palais à Paris", circa 1780. Silver-plated brass lined with black chagrin; closed length: 33 cm. Box attached. Rochon was the first to apply the phenomenon of double refraction to astronomy and the measurement of terrestrial distances. To this end, in 1777 he developed the first double-image prismatic micrometer using the birefringence of rock crystal: a light ray entering the prism is split in two. Rochon's telescope can be used to measure the distance to an object whose size is known, or the size of the object if its distance is known. Optician Herbage was one of the first manufacturers of this revolutionary optical instrument. For example, Jefferson's copy of Rochon's telescope is also signed Herbage.
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