Question 838Navigation General

70% to pass

A marine sextant has the index arm set at zero and the reflected image of the horizon forms a continuous line with the actual image. When the sextant is rotated about the line of sight the images separate. The sextant has _______________.

A prismatic error
B centering error
C side error
D error of perpendicularity
AI Explanation

The correct answer is C) side error. When the reflected image of the horizon forms a continuous line with the actual image and the images separate when the sextant is rotated about the line of sight, it indicates the sextant has a side error. Side error is caused by the index mirror not being perfectly perpendicular to the frame of the sextant. The other options are incorrect because: A) Prismatic error is caused by the index glass not being parallel to the horizon glass. B) Centering error is caused by the center of the index mirror not being aligned with the center of the horizon mirror. D) Error of perpendicularity is caused by the horizon mirror not being perfectly perpendicular to the frame of the sextant.

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