. The Encyclopaedia Britannica; ... A dictionary of arts, sciences and general literature . e- GmbVtscope of 4-incnes aperture, which is mounted to rotate sideio-about its axis, the latter forming the polar axis. MM etaticis a plane mirror reflecting rays from a star S to the telescop»object-glass, so that its image can be viewed from the!-piec6 at E, The star is retained in the field bythe clock C. Stars of different declination can beviewed by rotating the mirror on its axis G, andin different hour angles by rotating the tubeupon its axis. The instrument in cannot command
. The Encyclopaedia Britannica; ... A dictionary of arts, sciences and general literature . e- GmbVtscope of 4-incnes aperture, which is mounted to rotate sideio-about its axis, the latter forming the polar axis. MM etaticis a plane mirror reflecting rays from a star S to the telescop»object-glass, so that its image can be viewed from the!-piec6 at E, The star is retained in the field bythe clock C. Stars of different declination can beviewed by rotating the mirror on its axis G, andin different hour angles by rotating the tubeupon its axis. The instrument in cannot command a view of theheavens between the elevated pole and thezenith unless the distance OG is madeoicccdingly great; even then only alimited range beyond the rcuith iapossible. The instrument is pri-marily intended for sclar spectro-scopy, and thus these draw-backs do not apply. Theresulting ad-/ ff vantage is. that the ob-•? _/ server may boin completedarkness andhis observa-tions are notinterrupted bychange of posi-tion. In Comptea Xioevj sEendiis for the equator-year 1883, vol iaicoadt. Fio. 81.—Gmbbs slderostatlc telescope. xcvi. pp. 735-741, M. Loewy gives an account of an instrumentwhich he calls an equatorial coud^, designed (1) to attain greaterstability and so to measure larger angles than is generally possiblewith the ordinary equatorial; (2) to enable a single astronomer topoint the telescope and make observations in any part of the sky-without changing his position; (3) to aboUah the usual expensivedome, and to substitute a covered shed on wheels (which can be maback at pleasure), leaving the telescope in the open air, the observeralone being sheltered. These conditions are fulfilled in the mannershown in fig. 32. EP is the polar axis, rotating on bearings at E andP. The object-glass ia at 0, the eye-piece at E. There is a planemirror at M, which reflects rays converging from the object-glaasto the eye-piece at E. A second mirror K, placed at 45° to thaoptical axis o
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Keywords: ., bookcentury1900, bookdecade1900, bookidencyclopaedi, bookyear1902
