On 14 January your 0550 ZT DR position is...

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Question 1 of 2066636eea28f7522a1c51aab6

On 14 January your 0550 ZT DR position is LAT 25°26.0' N, LONG 38°16.0' W. You observe an unidentified star bearing 004.5°T, at an observed altitude (Ho) of 40°10.0'. The chronometer reads 08h 48m 51s and is 01m 22s slow. What star did you observe?

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Question 1 of 20

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🔍 Key Concepts

• Time and date to GHA/Dec – Use the Nautical Almanac for 14 January and the corrected chronometer time to find the star’s approximate GHA and declination. • Assumed position and intercept – Use the DR (or an assumed position near it) plus the observed altitude and true bearing to see which catalog star fits that line of position. • Star identification by position – Compare the computed intercept and azimuth for each candidate star to the observed bearing 004.5°T and Ho 40°10.0'.

💭 Think About

• First, correct the chronometer time for its error and convert to GMT/UT, then find the approximate Local Hour Angle for each candidate star at your longitude. Which one places the star roughly to the north (004.5°T) of your vessel? • Think about the declination of each star: at latitude 25°N and altitude about 40°, which stars’ declinations and hour angles could reasonably produce that observed altitude? • If you sketch the situation, which star choice would have an azimuth closest to 004.5°T from your DR position at that time?

✅ Before You Answer

• Be sure you apply the chronometer error (slow/fast) in the correct direction before entering the Nautical Almanac. • Verify you are using the correct date and hour block in the Almanac tables for 14 January and not accidentally using the previous or next day. • Double-check that the computed azimuth (Zn) for your candidate star is consistent with a bearing of about 004.5°T and that the computed altitude is close to 40°10.0'.

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