You observe the star Antares at a sextant altitude (hs) of 38°18.7' on 28 February. The index error is 2.4' on the arc. The height of eye is 40 feet (12.2 meters). What is the observed altitude (Ho)?

Correct Answer: Option A — 38°09.0'

Apply index error (on = add) to the sextant altitude. Subtract the dip correction for a 40-foot height of eye. Apply the refraction correction for stars from the Nautical Almanac. The resulting observed altitude (Ho) is 38°09.0', following standard Bowditch celestial navigation reduction procedures for stellar observations.