On 29 April your 1913 zone time DR position...

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Question 1 of 2066636eea28f7522a1c51add9

On 29 April your 1913 zone time DR position is LAT 22°09.0'N, LONG 56°16.0'W. At that time you observe Polaris with a sextant altitude (hs) of 22°25.8'. The chronometer time of the sight is 11h 11m 14s, and the chronometer error is 02m 18s slow. The index error is 1.5' off the arc, and the height of eye is 61.5 feet. What is your latitude by Polaris?

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🔍 Key Concepts

• Polaris latitude method – how Polaris altitude relates to observer’s latitude, including corrections for Polaris not being exactly at the pole • How to convert sextant altitude (hs) to observed altitude (ho): index correction, dip (height of eye), and other small corrections • Use of chronometer time and longitude to find LHA Aries/GHA Aries and apply the correct Polaris corrections from tables

💭 Think About

• First, carefully reduce hs to ho. Are you correctly applying index error that is off the arc and the dip for 61.5 feet? Check the sign of each correction. • Think about the relationship between the final corrected Polaris altitude and your latitude in this latitude range. Should latitude be slightly greater than, slightly less than, or very close to the observed altitude of Polaris? • Consider what role the date (29 April) and approximate local hour angle of Aries play in the Polaris correction tables. How big are those corrections likely to be at about 22°N, and in which direction do they usually shift the latitude?

✅ Before You Answer

• Double‑check the sign of index correction for 1.5' off the arc and ensure you compute the correct dip value for a height of eye 61.5 ft. • Confirm you converted chronometer time to GMT correctly using the given chronometer error (slow) before using it with your longitude. • When you have a candidate latitude, ask: is it consistent with the DR position (22°09.0'N) and with the approximate Polaris altitude you started with? Eliminate any choices that are clearly inconsistent.

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