At 1430 ZT on 16 April 1981, in DR position...

Question 1 of 2921866636eea28f7522a1c51aad4

At 1430 ZT on 16 April 1981, in DR position LAT 34° 03.8' N, LONG 061° 02.5' W, you observe an amplitude of the Moon. The center of the Moon is on the visible horizon and bears 095.2° psc. The variation is 12° W. What is the deviation?

Back

Question 1 of 29218

🔍 Key Concepts

• Amplitude of a celestial body at the visible horizon (relation between true bearing and true amplitude) • How to convert between compass, magnetic, and true bearings using variation and deviation • Sign convention for easterly vs westerly deviation

💭 Think About

• From the observed compass bearing of the Moon on the visible horizon, what quantity do you get after applying the known variation of 12° W? • How do you obtain the true amplitude of the Moon at that time and latitude, and how is it related to the Moon’s true bearing when on the horizon? • Once you have both the true bearing and the magnetic bearing of the Moon, how do you determine the deviation and decide whether it is east or west?

✅ Before You Answer

• Be clear on the order: compass → magnetic → true, and which corrections (variation, deviation) go where. • Verify the sign for west variation in the relationship: True = Magnetic ± Variation. • Check the final step carefully: if the compass reads higher or lower than magnetic for that direction, does that correspond to E or W deviation?