Question 742Navigation General

70% to pass

Which of the four adjustable errors in the sextant causes side error?

A Elliptical centering error
B Index mirror not being perpendicular to the frame
C Horizon glass not being perpendicular to the frame
D Telescope not being parallel to the frame
AI Explanation

The correct answer is C) Horizon glass not being perpendicular to the frame. The horizon glass on a sextant must be perpendicular to the frame in order to avoid side error, which is an error in the measured angle caused by the horizon glass not being aligned properly. If the horizon glass is not perpendicular to the frame, it will introduce a systematic error in the angle measurement. The other options are incorrect because they do not directly cause side error. Elliptical centering error, index mirror not being perpendicular, and telescope not being parallel are other potential errors in sextant measurements, but they do not specifically result in side error.

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Official Resources
USCG Navigation Rules (COLREGS) 33 CFR Navigation Rules USCG National Maritime Center
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