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The 60-inch reflector. In 1885 Common embarked on building a 60-inch (150 cm) Newtonian reflecting telescope. He chose to buy the raw glass blank and do the grinding and polishing himself. The first mirror he made performed poorly, showing an elliptical deformation of the stars, causing him to fabricate a second mirror in 1890.
A short film was published in 1956 that featured the grinding of the 98-inch mirror blank for the Isaac Newton Telescope by Grubb Parsons. [10] (reflecting telescopes of this type need the glass blank ground into a precise shape, which can take years). The telescope's first light (first, first light) occurred in 1965, and it was dedicated in 1967.
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 alternative to the refracting telescope which, at that time, was a design that suffered from severe chromatic ...
Objective: The first lens or curved mirror that collects and focuses the incoming light. Primary lens: The objective of a refracting telescope. Primary mirror: The objective of a reflecting telescope. Corrector plate: A full aperture negative lens placed before a primary mirror designed to correct the optical aberrations of the mirror.
Parsons improved the techniques of casting, grinding and polishing large telescope mirrors from speculum metal, and constructed steam-powered grinding machines for parabolic mirrors. His 3 foot (91 cm) mirror of 1839 was cast in smaller pieces and then fitted together before grinding and polishing; its 1840 successor was cast in a single piece.
The term is applied to the fabrication of large telescope mirrors, where the natural paraboloid curve followed by the molten glass greatly reduces the amount of grinding required. Rather than being cast by pouring glass into a mold (with top and bottom), an entire turntable containing the peripheral mold, and the back pattern (a honeycomb ...
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