On 2 January your vessel's 1948 zone time...

Question 1 / 2066636eea28f7522a1c51ac2f

Question 1 of 2066636eea28f7522a1c51ac2f

On 2 January your vessel's 1948 zone time position is LAT 21° 42' S, LONG 39° 12' W, when an amplitude of the Sun is observed. The Sun's center is on the celestial horizon and bears 260° per standard magnetic compass. Variation in the area is 19° W. The chronometer reads 10h 44m 36s and is 03m 24s slow. What is the deviation of the standard magnetic compass?

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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 • How to use chronometer time, date, and DR position to get the Sun’s true amplitude from tables or formulas

💭 Think About

• From the DR position, date, and corrected chronometer time, determine the Sun’s declination and choose the correct table for amplitude (e.g., for latitude and declination of the same/opposite name). What is the Sun’s true amplitude? • Convert the Sun’s observed bearing of 260° per standard magnetic compass into an observed amplitude (degrees N or S of west). Then compare this with the computed true amplitude to find total compass error. • Once you have total compass error from the amplitude, carefully separate variation (given) and deviation (unknown), keeping track of East/West signs. Which way must deviation act so that variation plus deviation matches the total compass error you found?

✅ Before You Answer

• Be sure the chronometer correction (slow or fast) is applied with the correct sign before looking up GHA and declination. • Confirm that you are using the correct latitude (S) and declination name (N or S) when entering the amplitude table, since mixing names changes the sign of the amplitude. • When combining variation and deviation to match your total compass error, double‑check your East/West sign convention: remember the standard mnemonic like “True Virgins Make Dull Company” (TVMDC) to keep the order and signs straight.

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Question 1 of 20

4.3° E

4.3° W

5.1° E

5.1° W

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Question 1 / 2066636eea28f7522a1c51ac2f

Question 1 of 2066636eea28f7522a1c51ac2f

Back

Question 1 of 20

66636eea28f7522a1c51ac2f

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🔍 Key Concepts

💭 Think About

✅ Before You Answer

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