On 4 July your vessel's 1722 zone time DR position is LAT 34°30'S, LONG 174°48'E, when an amplitude of the Sun is observed. The sun's center is on the visible horizon and bears 282° per standard magnetic compass. Variation in the area is 17.2°E. The chronometer reads 05h 21m 48s and is 02m 01s fast. What is the deviation of the compass?

Question

On 4 July your vessel's 1722 zone time DR position is LAT 34&deg;30'S, LONG 174&deg;48'E, when an amplitude of the Sun is observed. The sun's center is on the visible horizon and bears 282&deg; per standard magnetic compass. Variation in the area is 17.2&deg;E. The chronometer reads 05h 21m 48s and is 02m 01s fast. What is the deviation of the compass?

Accepted Answer

Option A: 1.5&deg;W. Determine the Sun's true amplitude using the formula sin(Amp) = sin(Dec) / cos(Lat). Convert the true amplitude to a true bearing. The difference between the true bearing and the compass bearing (282°) is the total compass error. Subtracting the 17.2°E variation results in a deviation of 1.5°W.