On 22 May your 0437 DR position is LAT...

Question 1 of 31048nOhV8D3uDlm5uO0Ryybn

On 22 May your 0437 DR position is LAT 25°18.5'N, LONG 51°18.0'W. You observe an unidentified star bearing 116°T at an observed altitude (Ho) of 11°27.8'. The chronometer reads 07h 40m 40s, and is 03m 24s fast. What star did you observe?

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Question 1 of 31048

🔍 Key Concepts

• Chronometer correction and UTC – how to apply a chronometer that is fast or slow to get the correct time of observation • Sidereal Hour Angle (SHA) and Declination (Dec) – how star positions are given in the Nautical Almanac and how they relate to your DR latitude and LHA • Intercept method (altitude difference) – comparing computed altitude (Hc) for a candidate star with observed altitude (Ho) to see what matches

💭 Think About

• First, convert the chronometer reading to the correct UTC of the sight. Then think about how you get GHA Aries and then the GHA (or LHA) of each candidate star at that time. • From your DR position and each candidate star’s Dec, think about which stars are even reasonably visible at an altitude around 11° in your hemisphere and at that latitude. • For each candidate, conceptually compare what bearing and altitude you would expect from your DR position. Which one would plausibly be near a true bearing of 116° and low in the sky (about 11° high)?

✅ Before You Answer

• Be sure you are applying the chronometer correction in the correct direction (fast vs slow) to get the right UTC. • Check that your computed Local Hour Angle (LHA) for the candidate star is consistent with a true bearing near 116°T from your DR longitude. • Verify that the star’s declination sign (N or S) and magnitude make it a likely low-altitude star (Ho ≈ 11°) as seen from 25°N latitude.