On 22 March your 0519 DR position is LAT 27° 20.6' N, LONG 69° 25.6' W. You observe an unidentified star bearing 200° T at an observed altitude (Ho) of 33° 05.5'. The chronometer reads 10h 16m 47s, and is 02m 15s slow. What star did you observe?
• Local Mean Time (LMT) and converting chronometer readings to Greenwich Mean Time (GMT) using chronometer error • Determining GHA Aries and applying SHP (Sidereal Hour Angle) of stars to find assumed position and intercept • Comparing the calculated true bearing and intercept from star candidates with the observed bearing and Ho
• How do you correct the chronometer time, and then convert that time to GMT and then to LMT at your DR longitude? • Once you know the approximate LMT, which stars are likely to be visible at that date, time, and latitude, and how does their predicted bearing compare with your observed 200° T? • After computing a sight for each candidate star, which one gives an intercept and azimuth that best matches your observed Ho and bearing?
• Be sure you’ve correctly applied the chronometer error (slow/fast) sign when finding GMT. • Confirm that your DR longitude sign and direction (E/W) are used correctly when converting between GMT and LMT. • Verify that the computed azimuth (Zn) for the candidate star closely matches the observed true bearing of 200° T before deciding.
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