On 12 March your 1846 zone time DR position...

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Question 1 of 2066636eea28f7522a1c51aa65

On 12 March your 1846 zone time DR position is LONG 129°16.5'W. At that time you observe Polaris with a sextant altitude (hs) of 28°01.5'. The chronometer time of the sight is 03h 44m 10s, and the chronometer error is 01m 55s slow. The index error is 2.2' off the arc, and the height of eye is 59.8 feet (18.2 m). What is your latitude by Polaris?

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🔍 Key Concepts

• Polaris latitude method: Approximate latitude ≈ observed altitude of Polaris after applying corrections • Sextant corrections: Apply index correction, dip (height of eye), and altitude corrections to convert hs → Ho (observed altitude) • Adjusting for chronometer error and using the correct LHA of Aries/Polaris for the given date and longitude

💭 Think About

• How do you correctly convert sextant altitude (hs) of Polaris into observed altitude (Ho)? List each correction in order and its sign. • Once you have Ho, what additional small corrections are applied specifically for Polaris to arrive at latitude (such as polar distance and small tabular corrections)? • How does the date (12 March) and your longitude affect the local hour angle and the tabular corrections you must pick from the Nautical Almanac for Polaris?

✅ Before You Answer

• Be sure you have the correct index correction sign when the error is "off the arc" and apply it properly to hs. • Confirm you used the proper dip correction for 59.8 ft (18.2 m) and applied it with the correct sign (does it increase or decrease the sextant altitude?). • Verify you have selected the correct Polaris correction values from the Nautical Almanac for 12 March and for the LHA range corresponding to LONG 129°16.5'W at the corrected chronometer time.

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