On 22 July your 1759 DR position is LAT 24°...

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Question 1 of 2066636eea28f7522a1c51acfd

On 22 July your 1759 DR position is LAT 24° 50.2' S, LONG 05° 16.0' E. You observe an unidentified star bearing 293° T at an observed altitude (Ho) of 17° 52.8'. The chronometer reads 06h 01m 31s, and is 02m 15s fast. What star did you observe?

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🔍 Key Concepts

• Use the chronometer correction (fast/slow) to find the correct GMT of the sight • From date, time, and DR longitude, determine the Local Hour Angle (LHA) Aries and then the star’s LHA • Compare the approximate bearing and altitude from the sight with the catalog positions (GHA/Dec) of the candidate stars

💭 Think About

• How does a chronometer that is 02m 15s fast change the actual GMT you should use for the sight reduction? • Once you have LHA Aries, what is the next step to get the approximate position (Dec and LHA) of the star you observed? • Given your DR latitude (24° 50.2' S) and the star’s declination, which candidate star would naturally appear at about 17° 53' altitude on a bearing near 293° T?

✅ Before You Answer

• Be sure you apply the chronometer correction with the correct sign before entering the Nautical Almanac • Confirm the date in GMT after applying the time correction (watch out for possible date changes) • Check that the star you pick has a declination consistent with a southern latitude and produces both an altitude and azimuth close to the observed 17° 52.8' and 293° T

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