🔍 Key Concepts

• Sextant altitude (hs) vs. observed altitude (Ho) and the standard sequence of corrections • Meaning of index error off the arc and how to turn that into an index correction (IC) with the correct sign • Using dip (height of eye) correction and main altitude correction for the Sun’s lower limb from the Nautical Almanac

💭 Think About

• Write the full correction formula from hs to Ho and list each term in order, then decide for each term whether it is added or subtracted. • Think about whether an index error that is noted as "off the arc" makes the sextant read too high or too low, and therefore whether the correction must reduce or increase hs. • Estimate the size and sign of the dip correction for a 63‑foot eye height and compare how much each multiple‑choice option differs from the original hs reading.

✅ Before You Answer

• Confirm you have converted index error into index correction with the correct sign before applying it. • Be sure your dip correction is negative (brings the altitude down) and appropriate in size for 63 ft (around several minutes, not just 1–2'). • Use the correct main correction for the Sun’s lower limb, taken from the Nautical Almanac for about 38° altitude, and apply it with the correct sign before choosing the option.