Navigation Problems USCG Question #188 (Set 6)

On 6 March at 0550 zone time, morning stars were observed, and the vessel's position was determined to be LAT 23°56.0'N, LONG 27°19.0'W. Your vessel is steaming at 25.0 knots on a course of 149.0°T. A sextant observation of the Sun's lower limb is made at 0830 zone time. The chronometer reads 10h 32m 05s, and the sextant altitude is 31°31.5'. The index error is 2.5' on the arc, and the chronometer error is 01m 45s fast. Your height of eye on the bridge is 76.0 feet. What is the azimuth (Zn) of this sight using the assumed position?

Official USCG Answer & Rule Citation

Correct Answer: Option A — 112.8°T

Apply corrections to the sextant altitude using the Nautical Almanac to find Ho. Calculate the Sun's LHA and Declination for the GMT of observation. Using the assumed position, solve the navigational triangle via the cosine-haversine formula or sight reduction tables to determine the azimuth (Zn) of 112.8°T.

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