On 27 June your vessel's 0816 ZT DR position is LAT 22°14'S, LONG 53°52'W, when an azimuth of the Sun is observed. The chronometer time of the sight is 12h 15m 02s, and the Sun is bearing 047.5° per standard magnetic compass. The chronometer error is 00m 46s slow, and the variation in the area is 6.0°E. What is the deviation of the standard magnetic compass?
Official USCG Answer & Rule Citation
Correct Answer: Option D — 3.0°W
Compass error is found by comparing compass bearing with true bearing calculated from time, date, and position via celestial navigation. Subtracting variation from true bearing establishes magnetic bearing, revealing a standard magnetic compass deviation of 3.0°W.
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