On 8 February your 0800 zone time position...

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Question 1 of 2066636eea28f7522a1c51ae5b

On 8 February your 0800 zone time position is LAT 21°55'S, LONG 52°27'W. Your vessel is on course 056°T at a speed of 17.5 knots. An observation of the Sun's lower limb is made at 0938 zone time, and the observed altitude (Ho) is 46°06.5'. The chronometer reads 12h 37m 23s, and the chronometer error is 1m 24s slow. LAN occurs at 1243 zone time, and a meridian altitude of the Sun's lower limb is made. The observed altitude (Ho) for this sight is 83°56.1'. Determine the vessel's 1200 zone time position.

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Question 1 of 20

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🔍 Key Concepts

• Sun sight for longitude using chronometer time and zone time relationship • Using meridian altitude (LAN) of the Sun to find latitude • Computing DR (dead reckoning) position at the time of each sight and then advancing the first line of position to 1200

💭 Think About

• First, work out the DR track from 0800 to 0938 and from 0938 to 1200 using the given course and speed. How far do you travel in each interval, and what are the DR positions at each time? • For the 0938 sight, think about how you convert Ho to a line of position: what do you need from the Nautical Almanac (GHA, Dec) and how do you use chronometer time and its error to get the correct UT? • For the LAN sight at 1243 zone time, focus on how meridian altitude gives you latitude directly. How do you combine Ho, Sun’s declination, and the fact that it is meridian passage to find latitude, and what small run between 1200 and 1243 must you account for? • Once you have a latitude from LAN and a longitude from the morning sun sight, how do you advance/retard the corresponding LOPs to meet at 1200 and identify which multiple-choice position is consistent with your work?

✅ Before You Answer

• Double-check the time conversions: zone time → UT using the implied zone description from longitude, and then apply the chronometer error correctly (remember, "slow" vs "fast" direction). • Verify the sign and name of the Sun’s declination on 8 February and whether it is the same or contrary name to your DR latitude when using the meridian altitude formula. • Confirm that your run between sights (in nautical miles) matches the course and speed: small mistakes in distance or direction will shift both latitude and longitude and can help you eliminate wrong answers that are too far off on either coordinate.

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