On 31 May your vessel's 1420 zone time DR position is LAT 29°06'N, LONG 120°06'W, when an azimuth of the Sun is observed. The bearing of the Sun per standard magnetic compass was 255.3°. The chronometer time of the observation is 10h 17m 24s. The chronometer error is 02m 32s slow. The variation for this area is 12.9°E. What is the deviation of the standard magnetic compass?

Question

On 31 May your vessel's 1420 zone time DR position is LAT 29&deg;06'N, LONG 120&deg;06'W, when an azimuth of the Sun is observed. The bearing of the Sun per standard magnetic compass was 255.3&deg;. The chronometer time of the observation is 10h 17m 24s. The chronometer error is 02m 32s slow. The variation for this area is 12.9&deg;E. What is the deviation of the standard magnetic compass?

Accepted Answer

Option A: 2.5&deg;W. Determine the Sun's True Azimuth (Zn) for the observation time. Apply Variation (12.9°E) to the True Azimuth to find the Magnetic Azimuth. The difference between the Magnetic Azimuth and the Compass Bearing (255.3°psc) yields the deviation. Here, the calculated deviation is 2.5°W, aligning with the compass error formula.