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 197
tripod so that a plumb bobfrom the center of the instrument shall hang directly over the spot at which themeasurement is to be made. The legs of the tripod should be firnuy placed in suchmanner that the height shall be convenient for the observer and the instrumentshall be nearly level. Then the… … Fig. 62. MARINE SURVEYING. 191 and the cross hairs may be plainly seen and that the object will not appear to havemotion relatively to the cross hairs as the eye is moved to the right or left of theeyepiece. This last condition insures the cross hairs being at the common focus ofthe eyepiece and…
Navigation · Nautical astronomy
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