On Sunday, 8 November, your ship is enroute from Texas City, TX, to Portland, ME. At 0632 ZT, you fix your position at LAT 27°06'N, LONG 90°36'W. When the lower limb of the Sun was two-thirds of a diameter above the visible horizon, the Sun bore 105° per standard magnetic compass. At this time the chronometer read 12h 39m 20s and is 3m 20s slow. If the variation is 3°E, determine the deviation of the standard compass.
Official USCG Answer & Rule Citation
Correct Answer: Option A — 0.8°E
Calculate the Sun's declination and LHA to find the true azimuth. Since the Sun is above the horizon, apply a correction for altitude. Compare the resulting true azimuth to the magnetic bearing to find compass error. Subtract the 3°E variation from the compass error to determine the magnetic deviation.
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