On 13 October your vessel's 1722 zone time DR position is LAT 27°36'S, LONG 136°16'E, when an amplitude of the Sun is observed. The Sun's center is on the celestial horizon and bears 266° per standard magnetic compass. Variation in the area is 2°W. The chronometer reads 08h 24m 19s and is 01m 43s fast. What is the deviation of the standard magnetic compass?

Question

On 13 October your vessel's 1722 zone time DR position is LAT 27&deg;36'S, LONG 136&deg;16'E, when an amplitude of the Sun is observed. The Sun's center is on the celestial horizon and bears 266&deg; per standard magnetic compass. Variation in the area is 2&deg;W. The chronometer reads 08h 24m 19s and is 01m 43s fast. What is the deviation of the standard magnetic compass?

Accepted Answer

Option B: 2.8&deg;W. Calculate the Sun's declination for the time of observation. Use the amplitude formula sin(Amp) = sin(Dec) / cos(Lat) to find the true amplitude. Comparing this to the magnetic bearing of 266° and applying the 2°W variation results in a deviation of 2.8°W.