At 1435 ZT on 27 April, in DR position LAT...

Question 1 of 2707066636eea28f7522a1c51aad5

At 1435 ZT on 27 April, in DR position LAT 51° 56.8' N, LONG 150° 37.7' E, the Moon's upper limb is observed on the visible horizon, bearing 242.2° psc. Variation is 2° W. What is the deviation?

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Question 1 of 27070

At 1435 ZT on 27 April, in DR position LAT 51° 56.8' N, LONG 150° 37.7' E, the Moon's upper limb is observed on the visible horizon, bearing 242.2° psc. Variation is 2° W. What is the deviation?

🔍 Key Concepts

• True bearing vs. compass bearing and how to convert between them • Using variation (V) and deviation (D) to find compass error (CE) • The sign convention: "East is least, West is best" when moving between true, magnetic, and compass

💭 Think About

• First, think about how you would get the Moon’s true bearing at the time and DR position (what sight reduction or almanac information would you use?). • Once you have the true bearing, how do you use the given variation (2° W) to find the magnetic bearing? • Compare the magnetic bearing with the observed compass bearing (242.2° psc). From that comparison, which direction (E or W) must the deviation be, and what size in degrees?

✅ Before You Answer

• Be very clear on whether you are moving from True to Compass or from Compass to True in your working—this changes the sign of corrections. • Check that you apply variation (V) between True and Magnetic, and deviation (D) between Magnetic and Compass—don’t mix them up. • After you get a value for deviation, ask: does a West or East deviation make the compass read higher or lower than magnetic in this case? Make sure this matches your computed number.