On 10 August your vessel's 0426 zone time DR position is LAT 52°07'N, LONG 142°16'E, when an amplitude of the Sun is observed. The Sun's lower limb is about 20 minutes of arc above the visible horizon and bears 074.5° per standard compass. Variation in the area is 12°W. The chronometer reads 07h 24m 19s and is 02m 34s fast. Which of the following is the deviation of the standard compass?
Official USCG Answer & Rule Citation
Correct Answer: Option B — 1.3°E
Calculate the amplitude of the Sun using the formula sin(Amp) = sin(Dec) / cos(Lat). Adjust for the Sun's altitude using the correction tables in Bowditch. With a True amplitude of 085.8° and a variation of 12°W, the deviation is calculated as 1.3°E to match the observed 074.5°psc.
100% Free & Open Access — No daily limits, paywalls, or gated answers on BrightMariner.