On 22 June your 0424 DR position is LAT 26°18.5' N, LONG 124°18.2' W. You observe an unidentified star bearing 249°T at an observed altitude (Ho) of 52°50.7'. The chronometer reads 00h 23m 24s, and is 01m 32s slow. What star did you observe?
• Local Hour Angle (LHA) and how it is found from GHA and DR longitude • Using the Nautical Almanac daily pages and star pages to match time, LHA Aries, and star SHA/declination • Comparing your computed altitude (Hc) and azimuth with the observed altitude (Ho) and true bearing to identify a body
• First, correct the chronometer time and convert it to Greenwich Mean Time (GMT/UT), then find the Greenwich Hour Angle (GHA) of Aries for that moment. • Use your DR latitude and longitude with LHA Aries to compute which star(s) are in roughly the right direction (bearing about 249°T) and altitude (~53°). • From the star data (SHA and declination), compute Hc and Zn for each candidate star and see which one best matches the observed Ho and true bearing.
• Be sure you applied the chronometer correction correctly (remember it is "slow"), so you use the correct UT when entering the Nautical Almanac. • Confirm you are using the correct longitude convention when forming LHA (watch east/west signs carefully). • Double‑check that the computed altitude and azimuth for your final candidate are within a small, realistic difference of the observed Ho and 249°T bearing.
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