Word: refractor
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Dates: during 1900-1909
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...largest refracting lens in use is that of the great Yerkes telescope, with an aperture of forty inches. The Lick lens is thirty-six inches in aperture; the Royal Astrophysical Observatory at Potsdam has recently acquired a thirty- one inch photographic refractor; and the Pulkowa Observatory has a thirty inch lens, made by the late Alvan Clark of Cambridge. Greenwich and Washington have telescopes with apertures of twenty-six-inches. The largest instrument in the possession of the Harvard Observatory is the twenty four inch Bruce photographic telescope, mounted at Arequipa...