On 22 July your 0442 DR position is LAT...

Question 1 of 2707066636eea28f7522a1c51acf4

On 22 July your 0442 DR position is LAT 26°35.6'N, LONG 22°16.7'W. You observe an unidentified star bearing 104°T at an observed altitude (Ho) of 9°55.7'. The chronometer reads 05h 39m 03s, and is 03m 14s slow. What star did you observe?

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Question 1 of 27070

🔍 Key Concepts

• Chronometer correction and GMT – converting the given chronometer time and error into correct GMT for the sight • Estimated Position (EP) and assumed position – starting from the DR position to set up your sight reduction • Star identification using Hc/azimuth – comparing computed altitude and azimuth of candidate stars with the observed Ho and bearing

💭 Think About

• How do you correct the given chronometer time to obtain the actual GMT of the sight, and why does the sign of the chronometer error matter? • Once you have GMT and DR position, what tables or methods would you use to find which stars are available, and how would you predict their altitude and azimuth? • For each candidate star, how can you compare its computed altitude (Hc) and true bearing (Zn) to the observed Ho and bearing to rule it in or out?

✅ Before You Answer

• Be sure you apply the chronometer error with the correct sign to get GMT • Verify that your LHA (Local Hour Angle) and Dec (Declination) for each candidate star match the correct date and time (22 July) • Confirm that the computed altitude and azimuth for the star you select closely agree with the observed Ho and true bearing (within typical sight reduction differences)