On 10 February in DR position LAT 25°32.0'N,...

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Question 1 of 2066636eea28f7522a1c51a9c6

On 10 February in DR position LAT 25°32.0'N, LONG 135°15.0'E, you observe an amplitude of the Sun. The Sun's center is on the celestial horizon and bears 109°psc. The chronometer reads 09h 43m 25s and is 03m 20s fast. Variation in the area is 4.5°W. What is the deviation of the standard magnetic compass?

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Question 1 of 20

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🔍 Key Concepts

• Amplitude of the Sun and how it is used to find compass error • Relationship between true bearing, magnetic bearing, variation, and deviation • Corrections to time and the Sun’s declination on the given date and longitude

💭 Think About

• How do you convert the observed azimuth/amplitude (in psc, per standard compass) into a value you can compare with a calculated true amplitude? • Which corrections must be applied in order: time, longitude, declination, or variation/deviation, and where does each one enter the problem? • Once you have true bearing of the Sun and the compass bearing, how do you determine whether the resulting deviation is labeled East or West?

✅ Before You Answer

• Be sure you are using the correct formula for amplitude (involving latitude and declination) and the correct sign for N/S and E/W. • Confirm that you have correctly adjusted the chronometer time (accounting for it being fast) and converted to the proper zone/Greenwich hour angle needed to get the Sun’s declination. • Before choosing an answer, verify the final step: True = Magnetic + Variation and Magnetic = Compass + Deviation, and check your sign convention carefully.

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