Robert-Aglaé Cauchoix (24 April 1776 – 5 February 1845) was a French

optician An optician, or ''dispensing optician'', is a technical practitioner who designs, fits and dispenses lenses for the correction of a person's vision. Opticians determine the specifications of various ophthalmic appliances that will give the nec ...

and instrument maker, whose

lenses A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements ...

played a part in the race of the

great refractor Great refractor refers to a large telescope with a lens, usually the largest refractor at an observatory with an equatorial mount. The preeminence and success of this style in observational astronomy defines an era in modern telescopy in the 19t ...

telescopes in the first half of the 19th century.

Instruments

At first Cauchoix produced a wide range of scientific instruments including

barometer A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...

s and

micrometer Micrometer can mean: * Micrometer (device), used for accurate measurements by means of a calibrated screw * American spelling of micrometre The micrometre ( international spelling as used by the International Bureau of Weights and Measures; ...

s, but he soon specialized in optics, making

spherometer A spherometer is an instrument used for the precise measurement of the radius of curvature of a sphere or a curved surface. Originally, these instruments were primarily used by opticians to measure the curvature of the surface of a lens. Backgr ...

s and objectives. He made a

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to obse ...

for the

Paris Observatory The Paris Observatory (french: Observatoire de Paris ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centers in the world. Its hist ...

in 1820 and in 1825 he made a 6.5 inch (16.5 cm)

refractor A refracting telescope (also called a refractor) is a type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope). The refracting telescope design was originally used in spyglasses and ...

for the observatory of the

Collegio Romano The Roman College ( la, Collegium Romanum, it, Collegio Romano) was a school established by St. Ignatius of Loyola in 1551, just 11 years after he founded the Society of Jesus (Jesuits). It quickly grew to include classes from elementary school t ...

, a Jesuit academy in

Rome , established_title = Founded , established_date = 753 BC , founder = King Romulus ( legendary) , image_map = Map of comune of Rome (metropolitan city of Capital Rome, region Lazio, Italy).svg , map_caption ...

. In the

Royal Observatory, Greenwich The Royal Observatory, Greenwich (ROG; known as the Old Royal Observatory from 1957 to 1998, when the working Royal Greenwich Observatory, RGO, temporarily moved south from Greenwich to Herstmonceux) is an observatory situated on a hill in ...

an 1838 instrument named the Sheepshanks telescope includes an objective by Cauchoix. The Sheepshanks had a 6.7 inch (17 cm) wide lens, and was the biggest telescope at Greenwich for about twenty years. An 1840 report from the Observatory noted of the then-new Sheepshanks telescope with the Cauchoix doublet:

Great refractors

Although the

reflector telescope A reflecting telescope (also called a reflector) is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century by Isaac Newton as an alternati ...

was invented in the second half of the 18th century, technological difficulties made the refractor the telescope of choice until the mid-1850s. Improvements in lens production, like the introduction of the

achromatic lens An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths (typically red and blue) into focus on the same plane. The most com ...

John Dollond John Dollond FRS (10 June O.S. (21 June N.S.) 170630 November 1761) was an English optician, known for his successful optics business and his patenting and commercialization of achromatic doublets. Biography Dollond was the son of a Hugu ...

, spawned an

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An ...

size race that started in the early 1820s with a telescope made by the

German German(s) may refer to: * Germany (of or related to) **Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ger ...

optician

Joseph von Fraunhofer Joseph Ritter von Fraunhofer (; ; 6 March 1787 – 7 June 1826) was a German physicist and optical lens manufacturer. He made optical glass, an achromatic telescope, and objective lenses. He also invented the spectroscope and developed diffr ...

. Cauchoix must be credited holding the lens size record three times this period. In 1831, Cauchoix made a 13.3 inch (almost 33.8 cm) refractor for the

Irishman The Irish ( ga, Muintir na hÉireann or ''Na hÉireannaigh'') are an ethnic group and nation native to the island of Ireland, who share a common history and culture. There have been humans in Ireland for about 33,000 years, and it has been c ...

Edward Joshua Cooper Edward Joshua Cooper (May 1798 – 23 April 1863) was an Irish landowner, politician and astronomer from Markree Castle in County Sligo. He sat in the House of Commons of the United Kingdom from 1830 to 1841 and from 1857 to 1859, but is best ...

, who used it to observe

Halley's Comet Halley's Comet or Comet Halley, officially designated 1P/Halley, is a List of periodic comets, short-period comet visible from Earth every 75–79 years. Halley is the only known short-period comet that is regularly visible to the naked eye fr ...

in 1835 and a

solar eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of the Earth, totally or partially. Such an alignment occurs during an eclipse season, approximately every six mo ...

in 1836. In 1829, Cauchoix made an 11.75 inch lens for a French customer, but sold it to the British

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either o ...

James South Sir James South FRS FRSE PRAS FLS LLD (October 1785 – 19 October 1867) was a British astronomer. He was a joint founder of the Astronomical Society of London, and it was under his name, as President of the Society in 1831, that a peti ...

. South used it for his new telescope, which he found defective due to problems with the

equatorial mount An equatorial mount is a mount for instruments that compensates for Earth's rotation by having one rotational axis, the polar axis, parallel to the Earth's axis of rotation. This type of mount is used for astronomical telescopes and cameras. Th ...

. In 1838, this telescope was dismantled, but the lens by Cauchoix served in other instruments until 1989.

References

External links

Picture of Edward Cooper's telescope

London Science Museum The Science Museum is a major museum on Exhibition Road in South Kensington, London. It was founded in 1857 and is one of the city's major tourist attractions, attracting 3.3 million visitors annually in 2019. Like other publicly funded ...

. {{DEFAULTSORT:Cauchoix, Robert-Aglae 1776 births 1845 deaths 18th-century French people 19th-century French engineers French scientific instrument makers Telescope manufacturers

Instruments

Great refractors

See also

References

External links