On 13 June your 0445 DR position is LAT 20°...

Question 1 of 2707066636eea28f7522a1c51aa91

On 13 June your 0445 DR position is LAT 20° 12.0' N, LONG 44° 45.0' W. You observe an unidentified star bearing 168° T at an observed altitude (Ho) of 38° 56.0'. The chronometer reads 07h 43m 20s, and is 01m 39s slow. Which star did you observe?

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Question 1 of 27070

🔍 Key Concepts

• Greenwich Hour Angle (GHA) and how to correct it using chronometer time and chronometer error • Relationship between Local Hour Angle (LHA), GHA Aries, and a star’s Sidereal Hour Angle (SHA) • How a star’s declination and its LHA relate to an observed altitude (Ho) near your DR position

💭 Think About

• How do you convert the given chronometer time and its error into the correct UT (Universal Time) for entering the Nautical Almanac? • Once you have GHA Aries for that time, how do you find the LHA Aries at your DR longitude, and then relate that to each star’s SHA from the star list? • Given your DR latitude and the observed altitude (Ho), which candidate star’s declination and position in the sky (south of you at bearing 168° T) makes the most geometric sense?

✅ Before You Answer

• Be sure you apply the chronometer error with the correct sign (a slow chronometer vs. a fast one). • Verify that your LHA of the star places it generally to the south of your DR position (bearing 168° T), not to the north or on the wrong side of the meridian. • Check that the star’s computed altitude (Hc) for its SHA/Dec is reasonably close to the observed 38° 56.0'; large discrepancies indicate the wrong star.