The index arm has a spirit level to allow the navigator to ensure that the index is horizontal even when he cannot see the horizon.
12.
Smith called the instrument's index arm a " label ", in the manner of Elton for his mariner's quadrant.
13.
After determining the sun's altitude with the help of the plumb, time was calculated graphically with the help of the index arm ."
14.
An instrument invented by the mathematician and astronomer Bhaskara II ( 1114 1185 CE ) consisted of a rectangular board with a pin and an index arm.
15.
The index arm includes a nonius { { # tag : ref | in fact, it may be a vernier scale referred to by the older, inexact name.
16.
The device consisted of three primary components, an index arm, a radial arm and a chords was used to convert a measurement of distance to a measurement of angle.
17.
The observer manipulates the index arm so the reflected image of the body in the horizon glass is just resting on the visual horizon, seen through the clear side of the horizon glass.
