On 11 May in DR position LAT 28°13.7'N, LONG 168°36.3'E, you observe an amplitude of the Sun. The Sun's center is on the celestial horizon and bears 283°psc. The chronometer reads 07h 13m 19s and is 02m 56s slow. Variation in the area is 13°E. What is the deviation of the standard magnetic compass?
• Amplitude of the Sun and how it is used to find compass error • Difference between true bearing, magnetic bearing, and compass bearing • How to apply variation and then solve for deviation
• How do you convert the Sun’s observed compass bearing (psc) into a true bearing using the date, latitude, and the Sun’s declination? • Once you know the true bearing of the Sun at the moment of observation, how do you compare it with the compass bearing to get the total compass error? • After finding total compass error, how do you separate it into variation and deviation, and decide whether each is east or west?
• Make sure you use the correct Sun’s declination for 11 May from the Nautical Almanac before computing the true amplitude. • Check your sign conventions carefully: does an observed bearing greater or less than the true bearing indicate east or west error? • Verify you are applying variation in the correct direction when going between true and magnetic: "east is least, west is best" for converting between them.
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