On 11 May in DR position LAT 37° 06.0' N,...

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Question 1 of 2066636eea28f7522a1c51aa1f

On 11 May in DR position LAT 37° 06.0' N, LONG 45° 45.0' W you observe an amplitude of the Sun. The Sun's center is on the visible horizon and bears 089.0° psc. The chronometer reads 07h 57m 06s and is 01m 48s slow. Variation in the area is 20.0° W. What is the deviation

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🔍 Key Concepts

• Amplitude of the Sun at rising/setting: relationship between latitude, declination, and true bearing • Conversion chain True → Magnetic → Compass using variation and deviation (TVMDC) • Using chronometer error to find correct GMT and then the Sun’s declination for the time of the observation

💭 Think About

• How do you get the Sun’s declination at the moment of observation from the given date, corrected GMT, and the Nautical Almanac? • Once you know latitude and declination, how do you compute the true amplitude (or use the amplitude tables) and then convert that amplitude into a true bearing of the Sun on the visible horizon? • After applying the given variation 20.0° W to convert between true and magnetic, how does comparing your computed magnetic bearing with the observed 089.0° psc lead you to the value and sign (E or W) of the deviation?

✅ Before You Answer

• Be sure you have corrected the chronometer: it is 01m 48s slow, so decide whether to add or subtract to get GMT. • Check the formula or table you use for amplitude: (\sin A = \frac{\sin d}{\cos L}) (with correct signs and N/S designation). • When determining deviation, carefully follow T → V → M → D → C in the correct direction and check whether the compass is east or west of magnetic.

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