Question 1626Navigation General

The correct answer is B) Vertical circles. In the horizon system of coordinates, the equivalent to the meridians on the Earth are the vertical circles. Vertical circles are great circles that pass through the zenith and nadir points of the observer's horizon. They are perpendicular to the horizon plane and intersect at the celestial north and south poles, just as meridians intersect at the geographic north and south poles on Earth. The other options are incorrect because: A) Horizon is the reference plane, not the equivalent to meridians; C) Hour circles are used to measure time, not spatial coordinates; and D) Celestial meridians are a different coordinate system not directly related to the horizon system.