American practical navigator: an epitome of navigation and nautical astronomy (1914)
Bowditch, Nathaniel, 1773-1838, Logan, George Wood, 1868-1915, United States. Navy Dept. Bureau of Equipment · Washington, Govt. Print. Off · leaf 104
glass, withperfectly parallel faces. If they are at all prismatic, the observed altitude will beerroneous. The error may be removed by observing a second altitude with the roofreversed, and, in general, by taking one-half of a set of observations with the roof inone position and the other half with… … 98 INSTRUMENTS EMPLOYED IN NAUTICAL ASTRONOMY. 257. In setting up an artificial horizon, care should be taken that the basin isfree from dust and other foreign matter, as small particles floating upon the surfaceof the mercury interfere with a perfect reflection. The basin should be so placedthat…
Navigation · Nautical astronomy
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