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Frederick William Herschel [2] [3] KH, FRS (/ ... Herschel discovered that unfilled telescope apertures can be used to obtain high angular resolution, ...
Many of the largest were metal mirror reflectors, some of which had substational apertures even for the 20th century. One problem was that many instrument makers. including William Herschel, did not pass on their mirror-making craft, and by the next century reflectors had largely been passed over in favour of small achromats (2-lens refractors ...
William Herschel's 40-foot telescope, also known as the Great Forty-Foot telescope, was a reflecting telescope constructed between 1785 and 1789 at Observatory House in Slough, England. It used a 48-inch (120 cm) diameter primary mirror with a 40-foot-long (12 m) focal length (hence its name "Forty-Foot").
By itself, the diameter of the primary optics can be a poor measure of a telescope's historical or scientific significance; for example, William Parsons, 3rd Earl of Rosse's 72-inch (1.8 m) reflecting telescope did not perform as well (i.e. gather as much light) as the smaller silvered glass mirror telescopes that succeeded it because of the ...
This is a list of large optical telescopes.For telescopes larger than 3 meters in aperture see List of largest optical reflecting telescopes.This list combines large or expensive reflecting telescopes from any era, as what constitutes famous reflector has changed over time.
Early reflectors using speculum metal had some of the record-breaking apertures of the day, but not necessarily high performance. Starting in the 1860s metal coated glass ('Silver on glass') reflector telescopes proved more durable, for example the Crossley Reflector, which continued to be used and upgraded even into the 21st century.
It was discovered by William Herschel on October 6, 1784. [3] The galaxy is a member of the NGC 1023 group of galaxies in the Local Supercluster. It has an H II nucleus. [4] The object is visible in small to moderate size telescopes as a faint elongated smear of light with a dust lane visible in larger apertures.
The original New General Catalogue was compiled during the 1880s by John Louis Emil Dreyer using observations from William Herschel and his son John, among others.Dreyer had already published a supplement to Herschel's General Catalogue of Nebulae and Clusters (GC), [2] containing about 1,000 new objects.