On 29 June you observe the star Achernar at a sextant altitude (Hs) of 54°18.9'. The index error is 4.7' off the arc. The height of eye is 58 feet. What is the observed altitude (Ho)?

Correct Answer: Option A — 54°15.5'

Apply index error (off = subtract) to the sextant altitude. Subtract the dip correction for a 58-foot height of eye. Apply the refraction correction for stars from the Nautical Almanac. The resulting observed altitude (Ho) is 54°15.5', consistent with standard celestial navigation reduction procedures for stellar observations.