On 17 January your 0730 zone time position...

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Question 1 of 2066636eea28f7522a1c51ab46

On 17 January your 0730 zone time position was LAT 22° 26.0' N, LONG 152° 17.0' E. Your vessel was steaming on course 136° T at a speed of 17.0 knots. An observation of the Sun's lower limb was made at 1015 ZT. The chronometer read 00h 13m 23s and was slow 01m 49s. The observed altitude (Ho) was 40° 25.7'. LAN occurred at 1222 zone time. The observed altitude (Ho) was 47° 48.1'. What was the longitude of your 1200 zone time running fix?

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🔍 Key Concepts

• Sun sight running fix using a morning sight advanced to LAN/1200 • Conversion of chronometer time to GMT and then to Local Hour Angle (LHA) for the Sun • Relationship between change in observed altitude (Ho) and the east–west shift in longitude over time

💭 Think About

• First, focus on the 1015 ZT sight: how do you turn the chronometer reading plus its slow error into the correct UTC/GMT for that sight? Then, how do you use that time to find GHA and determine an initial longitude line? • Think about LAN at 1222 ZT: what does the Sun being at its highest point tell you about your meridian (longitude) at that moment? How does LAN time compare with 1200 ZT, and what does that imply about where you are east or west? • Between 0730 and 1200 ZT, you are steaming on 136° T at 17 knots. How far (in NM) do you travel, and how much of that distance is effectively east–west? How does that projected motion shift your morning longitude line to give the 1200 running fix?

✅ Before You Answer

• Be sure you correctly apply the chronometer error (slow/fast) with the right sign before entering the Nautical Almanac for GHA and declination. • Double‑check you are using the correct zone description/sign to relate zone time (ZT) to UTC/GMT; a sign error here will shift all candidate longitudes in the same direction. • When advancing the 1015 Sun line to 1200, carefully compute the track components (east–west vs north–south) from course 136° T and 17 knots; confirm your total run in NM and that the longitude change you infer matches the direction of your vessel’s motion.

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