On 10 January at 0550 ZT, morning stars were...

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Question 1 of 2066636eea28f7522a1c51a9c8

On 10 January at 0550 ZT, morning stars were observed, and the vessel's position was determined to be LAT 25° 16.0' N, LONG 123° 18.0' W. Your vessel is steaming at 22.0 knots on a course of 295° T. A sextant observation of the Sun's lower limb is made at 0915 ZT. The chronometer reads 05h 14m 02s, and the sextant altitude is 24° 00.7'. The index error is 2.6' off the arc, and the chronometer error is 01m 34s slow. Your height of eye on the bridge is 55.0 feet. What is the azimuth (Zn) of this sight using the assumed position?

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🔍 Key Concepts

• Apply the 3 Ls (Label, Local, Longitude) to convert between zone time and GMT/UT correctly before entering the Nautical Almanac. • Use the assumed position from your DR (dead reckoning) at the time of the Sun sight, not the earlier star fix, when computing LHA and declination. • Remember the standard azimuth (Zn) procedure: compute Hc first from AP, then use latitude, declination, and local hour angle to determine Zn.

💭 Think About

• How do you advance the 0550 ZT position to 0915 ZT using the given course and speed to get the assumed latitude and longitude for the Sun sight? • Once you have GHA and declination of the Sun at the correct UTC, how do you form Local Hour Angle (LHA), and what does the sign of LHA tell you about which quadrant the azimuth will fall in? • Given that this is a morning Sun sight in the northern hemisphere with the vessel west longitude, should the true azimuth (Zn) be closer to due east, southeast, or southwest?

✅ Before You Answer

• Be sure you have corrected chronometer time to UTC, including chronometer error, before entering the Nautical Almanac. • Verify that you converted the index error and height of eye correctly when finding Ho; even though Ho is not directly used for Zn, this keeps your work consistent. • When choosing among the multiple‑choice Zn values, double‑check which quadrant (NE, SE, SW, NW) your Sun should be in at the time and place of observation so you can eliminate impossible answers.

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