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 98
sure for any change of inclination of the index mirror; a reading glass,R, attached to the index bar and turning upon a pivot, S, facilitates the reading ofvernier and scale. The index mirror, M, is attached to the head of the index bar, withits surf ace perpendicular to the plane of the… … FIG. 32. 92 INSTRUMENTS EMPLOYED IN NAUTICAL ASTRONOMY. horizon is observed in measuring altitudes of celestial bodies; it is provided withscrews, by which its perpendicularity to the plane of the instrument may beadjusted. At P and Q are colored glasses of different shades, which may be…
Navigation · Nautical astronomy
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