On 4 October your 1907 zone time DR position...

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Question 1 of 2066636ef128f7522a1c522da5

On 4 October your 1907 zone time DR position is LAT 25°15.0'S, LONG 105°44.0'E. At that time, you observe Deneb bearing 011.5°psc. The chronometer reads 00h 07m 42s, and the chronometer error is 00m 36s fast. The variation is 7.5°W. What is the deviation of the standard compass?

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🔍 Key Concepts

• Amplitude/azimuth of a star to find compass error • Relationship between true bearing, magnetic bearing, and compass bearing • Applying chronometer error and converting times for sight reduction

💭 Think About

• How do you turn the observed compass bearing of Deneb into a true bearing step-by-step? List each correction in order. • What role do GHA, Dec of Deneb, and your DR latitude/longitude play in finding the true azimuth of the star? • Once you know the true bearing, how do you compare it to the compass bearing to get total compass error, and then separate variation and deviation?

✅ Before You Answer

• Be sure your chronometer time is converted to correct UTC using the chronometer error. • Confirm you apply zone description and date correctly when entering the Nautical Almanac for GHA and Dec of Deneb. • After getting total compass error, carefully apply the known variation (7.5°W) with the correct sign convention to isolate deviation.

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