Question 1628Navigation General

The correct answer is B) the zenith and the north and south poles. The principal vertical circle is the great circle on the celestial sphere that passes through the zenith (the point directly overhead) and the north and south celestial poles. This circle is perpendicular to the horizon and is used as a reference for determining the altitude and azimuth of celestial bodies. The other options are incorrect because: A) The principal vertical circle does not necessarily pass through the celestial body itself, but rather through the zenith and the poles. C) The principal vertical circle is not parallel to the horizon, but rather perpendicular to it. D) The principal vertical circle is not defined in relation to the Greenwich meridian.