On 12 June your 1845 DR position is LAT 21°47'N, LONG 46°52'W when you observe a faint unidentifiable star through a break in the clouds. The star bears 282.5°T at a sextant altitude (hs) of 14°22.3'. The index error is 0.5'on the arc, and the height of eye is 45 feet. The chronometer reads 09h 43m 27s, and the chronometer error is 1m 46s slow. What star did you observe?
Official USCG Answer & Rule Citation
Correct Answer: Option A — Alhena
Convert chronometer time to GMT and determine LHA Aries. Using the Nautical Almanac and Pub. 229, calculate the star's position based on the observed altitude and azimuth. Alhena matches the calculated coordinates, confirming it as the observed star for the given DR position and time of observation.
100% Free & Open Access — No daily limits, paywalls, or gated answers on BrightMariner.