American practical navigator: an epitome of navigation and nautical astronomy (1914)
Bowditch, Nathaniel, 1773-1838, United States. Navy Dept. Bureau of Equipment, Logan, George Wood, 1868-1915 · Washington, Govt. Print. Off. · leaf 99
the reflectingsurfaces. Upon this fact the construction of the sextant is based. In figure 33, let B and C represent respectively the index mirror and horizonmirror of a sextant; draw EF perpendicular to B, and CF perpendicular to C; thenthe angle CFB represents the inclination of tlie two mirrors.… … INSTRUMENTS EMPLOYED IN NAUTICAL ASTRONOMY. 93 From the equality of the angles of incidence and reflection: ABE = EBC, and ABC = 2 EBC;BCF = FCD, and BCD = 2 BCF. From Geometry: ADC = ABC - BCD = 2 (EBC - BCF) = 2 CFB, which is the relation that was to be proved. 243. In the sextant, since the…
Navigation · Nautical astronomy
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