At 0520 zone time on 17 March, while taking...

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Question 1 of 2066636eea28f7522a1c51a841

At 0520 zone time on 17 March, while taking stars for a morning fix, you observe an unidentified star bearing 050°T, at an observed altitude (Ho) of 45°00.0'. Your DR position at the time of the sight is LAT 27°23.0'N, LONG 39°42.0' W. The chronometer time of the sight is 08h 22m 15s, and the chronometer error is 01m 45s fast. Your vessel is steaming on a course of 300°T at a speed of 18 knots. What star did you observe?

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Question 1 of 20

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🔍 Key Concepts

• Chronometer correction and conversion to GMT/UT from zone time and chronometer error • Using your DR position to compute Local Hour Angle (LHA) and computed altitude (Hc) for candidate stars • Comparing computed true bearing and altitude of each candidate star to the observed values to identify the body

💭 Think About

• First, what is the correct Greenwich time (UT) of the sight after you apply the chronometer error and relate it to the given zone time? • Given your DR latitude and longitude, how would you obtain the GHA and declination of each candidate star at that instant to compute an intercept or at least an Hc and Zn? • Once you have Hc and Zn for a candidate star, how do you decide whether that star matches your observed Ho = 45°00.0' and bearing 050°T?

✅ Before You Answer

• Be sure you apply the chronometer error with the correct sign (fast vs. slow) before using the time for any sight reduction. • Verify that your azimuth (Zn) for each candidate star is in the same quadrant and close to the observed 050°T bearing. • Check that the difference between Ho and Hc (intercept) is small for the correct star and significantly larger for the others.

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