On 28 November your vessel's 0652 DR position is LAT 37°30'N, LONG 124°12'W, when an amplitude of the Sun is observed. The Sun's center is on the visible horizon and bears 103° per standard magnetic compass. Variation in the area is 16.3°E. The chronometer reads 02h 54m 18s and is 02m 06s fast. What is the deviation of the compass?

Question

On 28 November your vessel's 0652 DR position is LAT 37&deg;30'N, LONG 124&deg;12'W, when an amplitude of the Sun is observed. The Sun's center is on the visible horizon and bears 103&deg; per standard magnetic compass. Variation in the area is 16.3&deg;E. The chronometer reads 02h 54m 18s and is 02m 06s fast. What is the deviation of the compass?

Accepted Answer

Option A: 2.5&deg;W. Find the Sun's declination for 28 November. Calculate the true amplitude using sin(Amp) = sin(Dec) / cos(Lat). Convert the amplitude to a true bearing. Apply the 16.3°E variation to the compass bearing of 103°psc to find the magnetic bearing. The difference between the true and magnetic bearings results in 2.5°W deviation.