On 6 March at 0550 zone time, morning stars...

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Question 1 of 2066636eea28f7522a1c51ae3a

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?

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🔍 Key Concepts

• Time conversions: Convert zone time to GMT/UTC using the correct zone description, then apply the chronometer error properly (fast vs slow). • Sextant corrections: Apply index correction, dip (height of eye), and main altitude corrections to get observed altitude (Ho). • Azimuth (Zn): Use the assumed position, Greenwich Hour Angle and declination of the Sun at the correct time, then a standard azimuth formula or table (like Pub. 249/229) to get Zn.

💭 Think About

• How do you determine the exact UTC of the sight from the given zone time, chronometer reading, and chronometer error? Walk through that sequence carefully. • Once you have the Sun’s GHA and declination at the correct time, how does your latitude and Local Hour Angle determine whether the azimuth should be more easterly or westerly, and roughly what range of bearings that implies? • Given your course (149° T) and the approximate Sun position in the morning at that latitude and longitude in early March, which answer choices seem more plausible as a morning Sun bearing?

✅ Before You Answer

• Be sure you apply index error with the right sign: "on the arc" vs "off the arc" changes whether you add or subtract. • Confirm your zone description sign for converting zone time to GMT/UTC. A wrong sign here will send the Sun to the wrong side of the sky. • Check that your assumed position is correctly chosen from your DR at 0830 ZT, not just the original 0550 position. Your Zn must be consistent with that assumed position.

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