On 31 October your 1700 zone time DR position is LAT 27°17.0'N, LONG 116°10.0'W, when an amplitude of the Sun is observed. The Sun's center is on the visible horizon and bears 246.5° per standard magnetic compass. Variation in the area is 8.5°E. The chronometer reads 01h 01m 23s and the chronometer error is 01m 54s slow. What is the deviation of the standard compass?
Official USCG Answer & Rule Citation
Correct Answer: Option C — 0.8°W
Determine the Sun's declination and GHA for the observation time. Calculate the true amplitude using sin(Amp) = sin(Dec) / cos(Lat). Convert the true amplitude to a true bearing. The difference between the true bearing and the compass bearing is the compass error. Subtract variation (E+) to isolate the deviation.
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