On 22 March your 0519 DR position is LAT 27°...

Question 1 of 2707066636eea28f7522a1c51ad09

On 22 March your 0519 DR position is LAT 27° 20.6' N, LONG 69° 25.6' W. You observe an unidentified star bearing 115° T at an observed altitude (Ho) of 54° 52.8'. The chronometer reads 10h 16m 47s, and is 02m 15s slow. What star did you observe?

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Question 1 of 27070

🔍 Key Concepts

• Applying chronometer error to get the correct UTC before entering tables • Using the Nautical Almanac to find GHA Aries and sidereal hour angle (SHA) and declination of candidate stars for the given date and time • Comparing computed altitude (Hc) and true bearing (Zn) of candidate stars with the observed altitude (Ho) and bearing to identify the star

💭 Think About

• How do you correct the chronometer time to find the actual UTC, and why is this step critical before doing anything with star data? • Once you have GHA Aries, how do you use local longitude and SHA to find a star’s local hour angle (LHA), and from that its computed altitude and azimuth? • When you compare the calculated altitude and azimuth of each candidate star to your observed Ho and bearing, what differences would convince you that a particular candidate is not the correct star?

✅ Before You Answer

• Be sure you have applied chronometer error with the correct sign (slow vs. fast) before entering the Almanac. • Confirm you are using SHA (not GHA) for the star and combining it correctly with GHA Aries and your longitude. • Double‑check that the computed Zn and Hc for the star you think it is are reasonably close to your observed bearing 115° T and Ho 54° 52.8'.