The telescope was used for over a century with some updates, but the original was an "achromatic doublet of 11.6 inches clear aperture and focal length 19ft 6in". ![]() In 1833 the Duke of Northumberland donated a Cauchoix of Paris objective lens to establish a large telescope for the new Observatory of Northumberland. This was the largest refractor in the world in the early 1830s, and Cooper used the telescope to sketch Halley's comet in 1835 and to view the solar eclipse of. By 1834 it was mounted on an equatorial mounting supplied by Thomas Grubb of Dublin. Cooper had acquired the largest lens in the world, made by Cauchoix of Paris, with an objective of 13.3 inches (~34.8 cm) for 1200 pounds, and he placed it as the centerpiece of the observatory. In the early 19th century a young Edward Joshua Cooper built in Ireland one of the most richly furnished astronomical observatories of the period. As telescopes became larger and longer, the relatively modest increases in aperture belied their enormous size, with moving weights in the multiple tons in domes several stories tall physically many of the biggest were larger than even some modern reflecting telescopes.īeginnings An observer looking through the Markree's Cauchoix great telescope Fraunhofer refractor of 1824, now an exhibit at the old Tartu Observatory museum in Estonia. A derivative instrument of refractors, the heliometer was used to measure for the first time the distance to another star by geometric parallax in the mid-1800s. Some noted accomplishments of refractors were the discovery of Neptune, the discovery of the Moons of Mars, and the compilation of various star catalogs. ![]() In modern times many of these functions are performed elsewhere and communicated locally. Whereas in the modern era aperture and location are important, the older style observatories were often located near towns because astronomy was only one function major tasks were simply to record the weather, make accurate determinations of location, and to determine the local time. However, many have also been shut down or moved due to their difficulty of use as telescopes. In modern times many large refractors have become important historical items, and are often used for public astronomy outreaches. Īn example of prime achievements of refractors, over 7 million people have been able to view through the 12-inch Zeiss refractor at Griffith Observatory since it opened in 1935 this is the most people to have viewed through any telescope. Pioneering work on astrophotography was done with great refractors. Great refractors were often used for observing double stars and equipped with a Filar micrometer. It was also popular to exhibit large refractors at international exhibits, and examples of this include the Trophy Telescope at the 1851 Great Exhibition, and the Yerkes Great Refractor at the 1893 World's Fair in Chicago.Ī great refractor was often the centerpiece of a new 19th century observatory, but was typically used with an entourage of other astronomical instruments such as a Meridian Circle, a Heliometer, an Astrograph, and a smaller refractor such as a Comet Seeker or Equatorial. Despite typical designs having smaller apertures than reflectors, great refractors offered a number of advantages and were popular for astronomy. They were often the largest in the world, or largest in a region. Great refractors were large refracting telescopes using achromatic lenses (as opposed to the mirrors of reflecting telescopes). ![]() The preeminence and success of this style in observational astronomy defines an era in modern telescopy in the 19th and early 20th century. Great refractor refers to a large telescope with a lens, usually the largest refractor at an observatory with an equatorial mount. Treptow telescope (aka Himmelskanone) did away with a dome, and the telescope tube extends above the building in this image Grande Lunette of Nice Observatory of 1886, with 76 cm aperture James Lick telescope of 1888, with 91 cm aperture
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