Question 1511Navigation General

The correct answer is A) 90° - Ho. Zenith distance is the angular distance between the zenith (the point directly overhead) and the celestial body being observed. It is calculated as 90° minus the body's altitude (Ho), which is the angular height of the celestial body above the horizon. The other options are incorrect because: B) Ho° + d is the total correction to be applied to the sextant altitude to obtain the true altitude. C) 90° - z is the body's altitude (Ho), not the zenith distance. D) 90° - d is the body's altitude (Ho), not the zenith distance.