Word: focal
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Dates: during 1880-1889
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...Bruce, of New York, for a photographic telescope. The instrument will be made with a double lens, a new form not yet adopted by European astronomers, but considered by Professor Pickering far superior to single lens telescopes. It will have an aperture of twenty-four inches. Its focal length will be short, and consequently it will include a large area of the sky at once, and will also obtain images of very faint stars and nebulae. With this telescope, Professor Pickering expects to accomplish as much as seventeen other observatories working together according to a plan recently matured at Paris...
...Appointments of cabinet officers would be made on grounds of efficiency and not from political or focal considerations:- International Review pp. 157-1603; The Political Working of Our Government, pp. 8-9; Nation...
...optical parts of the telescope are three-the eye-piece, the object glass, which is twelve inches in diameter and a plain mirror of eighteen inches in diameter, set in front of the object glass. Focal length is sixteen and a half feet. The telescope tube is rested permanently upon two stone piers, one near each end, and twelve feet apart. About five feet of the length of the tube projects into the observatory building and the remainder is out of doors...
...this means an instant comparison can be secured between the pole star, as a standard, and the object of investigation, which is to be classified. The polar telescope has an aperture of five inches and a focal length of about seven feet...
...which can be transformed at will from a "photographic" to a "visual" lens by simply turning over the crown-glass lens and changing its distance from the flintglass lens. The Clarks have made for Professor Pickering a lens of this construction with an aperture of thirteen inches and a focal length of fifteen feet...