Question 1771Navigation General

The correct answer is B) 90° - Ho. The radius of the circle of equal altitude is determined by the formula 90° - Ho, where Ho is the observed altitude of the celestial body. This formula is derived from the fact that the circle of equal altitude is a small circle on the celestial sphere that is perpendicular to the observer's vertical circle. The radius of this circle is equal to the complement of the observed altitude (90° - Ho). The other options are incorrect because they do not accurately represent the formula for determining the radius of the circle of equal altitude.