On 16 February your 1845 ZT DR position is...

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Question 1 of 2066636eea28f7522a1c51ab0f

On 16 February your 1845 ZT DR position is LAT 25°50.5'N, LONG 46°24.0'W. At that time, you observe Polaris with a sextant altitude (hs) of 26°25.5'. The chronometer time of the sight is 09h 47m 30s and the chronometer error is 02m 16s fast. The index error is 2.5' off the arc, and the height of eye is 55.0 feet. What is your latitude by Polaris?

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🔍 Key Concepts

• Polaris latitude method (approximate latitude ≈ corrected altitude of Polaris, with small corrections) • How to apply sextant corrections: index error, height of eye (dip), and main altitude corrections to get Ho • Effect of chronometer error and time on the Polaris corrections from the Nautical Almanac

💭 Think About

• First, work step-by-step from hs to Ho. Which corrections increase the altitude and which decrease it? • Think about how the latitude from Polaris compares to Ho: is it usually exactly equal, slightly greater, or slightly less? Why? • Consider whether date and longitude (LHA Aries / GHA) cause a small positive or negative correction to the Polaris latitude, and estimate its likely size.

✅ Before You Answer

• Be sure the index error sign is handled correctly: "off the arc" vs "on the arc" changes whether you add or subtract • Confirm you used the correct dip correction for 55 ft and subtracted it from the sextant altitude • Verify that any Polaris table corrections you apply (for date and hour) are of the right order of magnitude (a few minutes, not whole degrees).

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