At 1523 ZT on 14 June, in DR position LAT...

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Question 1 of 2066636eea28f7522a1c51aaf9

At 1523 ZT on 14 June, in DR position LAT 31° 58' S, LONG 48° 42' W you observe an amplitude of the Moon. The center of the Moon is on the visible horizon and bears 118.0° psc. The variation is 10° W. What is the deviation?

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Question 1 of 20

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🔍 Key Concepts

• Amplitude of the Moon and how it is used to find compass error • Relationship between true bearing, magnetic bearing, variation, and deviation • Converting from psc (per standard compass) to true using the correct sign convention

💭 Think About

• From the observed amplitude and date/position, what is the Moon’s true amplitude (east or west of true north/south)? • How do you go from true bearing to compass bearing when variation and deviation are involved? Write out the usual TVMDC relationship and be careful with signs. • Once you know the total compass error from the amplitude, how do you separate it into variation and deviation?

✅ Before You Answer

• Be sure whether the Moon’s amplitude is measured from true east/west toward north/south, not from north like an azimuth. • Check the sign of west variation in your TVMDC work – does west variation make magnetic greater or less than true? • After finding deviation, verify whether it should be labeled E or W by seeing which way the compass is in error (i.e., does it read too high or too low compared with true?).

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