Question 1378Navigation General

A) principal vertical circle is the correct answer. The azimuth angle of a sun sight is always measured from the principal vertical circle, which is the great circle passing through the zenith and the north and south points of the horizon. This is the standard reference for measuring azimuth angles in celestial navigation. The other options are incorrect because: B) Greenwich meridian is used to measure longitude, not azimuth. C) The prime vertical circle is the great circle passing through the east and west points of the horizon, perpendicular to the principal vertical. D) The first point of Aries is the celestial reference point for measuring right ascension, not azimuth.