On 22 April your 1852 DR position is LAT...

Question 1 of 2707066636eea28f7522a1c51acdf

On 22 April your 1852 DR position is LAT 23°54.5'N, LONG 117°36.8'W. You observe an unidentified star bearing 248°T at an observed altitude (Ho) of 25°00.9'. The chronometer reads 02h 54m 53s, and is 02m 51s fast. What star did you observe?

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Question 1 of 27070

🔍 Key Concepts

• Chronometer correction and converting chronometer time to Greenwich Mean Time (GMT/UT1) • Using DR position, time, and altitude (Ho) to select the most likely star from a list using a Nautical Almanac/star tables • Checking that the true bearing and altitude make sense for that star from the given latitude/longitude and date

💭 Think About

• First, apply the chronometer error (fast/slow) to find the correct GMT of the sight. How does this time compare to evening/morning twilight at your DR position on 22 April? • From your DR latitude 23°54.5'N and the star’s observed bearing 248°T (about west-southwest), what approximate declination (north/south of the equator) would you expect the star to have? • Compare which of the listed stars would be visible at about 25° altitude in that direction at that time and date for this latitude. Which stars are even above the horizon there?

✅ Before You Answer

• Be sure you applied the chronometer correction in the correct direction (fast vs. slow). • Verify whether each star choice is north or south of the celestial equator, and whether that matches the expected sky area from 24°N latitude on that bearing. • Check if the Local Hour Angle (LHA) and declination for each candidate on 22 April at the computed GMT would place the star near 25° altitude and bearing 248°T from the DR position.