On 4 October, your 0734 zone time DR position is LAT 24°11.0'N, LONG 162°34.0'E. At that time, you observe the Sun bearing 105.5°psc. The chronometer reads 08h 36m 11s, and the chronometer error is 01m 46s fast. The variation is 7°W. What is the deviation of the standard compass?
• Compass deviation vs magnetic variation vs gyro error • Converting a pelorus/psc bearing to a true bearing using deviation and variation • Using the Sun’s calculated true bearing at a given time and position to back out unknown deviation
• How do you correct a standard compass (psc) bearing step-by-step to get a true bearing? List the sequence and the sign (+E / −W) at each step. • From your DR position, corrected time, and date, what is the Sun’s true bearing at that moment? Once you have that, how can you compare it to your observed compass bearing? • If your compass is reading higher or lower than the true bearing, in which direction (E or W) does that indicate the deviation is?
• Be sure you apply the chronometer error correctly to get the right UTC before using sight reduction tables/software. • Check that you use the correct sign for variation 7°W when going between true and magnetic. • When comparing true and compass bearings, verify which form of the memory aid (“Can Dead Men Vote Twice At Elections” or similar) you are using so the order of corrections is consistent.
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