On 11 May your vessel's 1839 ZT position is...

Question 1 / 2066636eea28f7522a1c51aa20

Question 1 of 2066636eea28f7522a1c51aa20

On 11 May your vessel's 1839 ZT position is LAT 17°30'N, LONG 63°55'W, when an amplitude of the Sun's center is observed on the celestial horizon bearing 301° per standard magnetic compass. Variation for this area is 10.5°W. The chronometer reads 10h 37m 10s and is 02m 08s slow. What is the deviation of the compass?

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🔍 Key Concepts

• Amplitude of the Sun to find compass error (difference between true bearing and compass bearing) • Converting local zone time (ZT) and chronometer time to get correct Greenwich Hour Angle (GHA) and declination from the Nautical Almanac • Relationship between variation, deviation, and compass error: True – Var – Deviation = Compass (or its equivalent form)

💭 Think About

• From the date, approximate the Sun’s declination and decide whether you should use rising or setting amplitude formula based on the observed bearing • Compute the Sun’s true amplitude from latitude and declination, then compare it with the observed amplitude to get compass error (east or west) • Once you have compass error, use the known variation to isolate the unknown deviation and determine if it is east or west

✅ Before You Answer

• Be sure you’re using the correct signs (N/S for latitude and declination) and the proper formula for northern vs. southern hemisphere and rising vs. setting Sun • Confirm your conversion from ZT to GMT/UT using the correct time zone and chronometer correction before taking almanac data • Carefully check the east/west sense: whether an indicated error means the compass is least or greatest and how that translates into east or west deviation

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Question 1 of 20

2.5°W

2.0°W

1.5°W

2.0°E

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Question 1 / 2066636eea28f7522a1c51aa20

Question 1 of 2066636eea28f7522a1c51aa20

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Question 1 of 20

66636eea28f7522a1c51aa20

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🔍 Key Concepts

💭 Think About

✅ Before You Answer

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