🔍 Key Concepts

• Index error correction: Understand how to apply an error that is "off the arc" versus "on the arc" to the sextant altitude (hs). • Dip (height of eye) correction: Know that this correction is always subtractive and depends on height of eye in feet or meters from the sight reduction tables or formula. • Total correction for Sun’s lower limb: Combine dip, refraction, and semidiameter (and small parallax) from the Nautical Almanac for the correct date to get Ho.

💭 Think About

• Start from hs and apply the index error in the correct direction to get the apparent altitude (ha). Ask yourself: does "off the arc" make the sextant read too high or too low? • Use the given height of eye to find dip and apply it to ha to get the corrected sextant altitude (he). Is dip making the altitude larger or smaller? • For the Sun’s lower limb on 5 April, determine the sign (add or subtract) and approximate size of the total Sun correction. Combine all corrections step by step and see which choice is closest.

✅ Before You Answer

• Be sure about the sign of index error: "off the arc" vs "on the arc" — this is critical. • Confirm that dip is always subtracted from ha, regardless of the body observed. • Estimate the magnitude of total Sun correction for an altitude near 58° and check if your final Ho is reasonable compared with the original hs (it should not differ by several whole degrees).