You observe the star Deneb at a sextant altitude (hs) of 48°34.8' on 16 December. The index error is 4.0' off the arc. The height of eye is 58 feet. What is the observed altitude (Ho)?

Correct Answer: Option B — 48°30.5'

Calculate Ho by applying the index error (off the arc is plus) to the sextant altitude. Subtract the dip correction for a 58-foot height of eye and the refraction correction from the Nautical Almanac. The resulting observed altitude is 48°30.5', following standard Bowditch correction procedures for celestial observations.