You observe the lower limb of the Sun at a sextant altitude (hs) of 42°44.0' on 22 June. The index error is 0.8' off the arc. The height of eye is 70 feet (21.3 meters). What is the observed altitude (Ho)?

Correct Answer: Option B — 42°51.7'

Apply index error (off the arc is additive) to hs. Subtract dip (based on 70ft height of eye) and apply refraction and semi-diameter corrections from the Nautical Almanac. The sum of these corrections to the lower limb results in an observed altitude (Ho) of 42°51.7', following standard Bowditch reduction.