The correct answer is: C. Declination and right ascension system.
The declination and right ascension system is the most convenient coordinate system for specifying the relative positions of heavenly bodies on the celestial sphere because it is a spherical coordinate system. This means that it can be used to specify the position of any object on the celestial sphere, regardless of its location in the sky.
The declination is the angular distance of a celestial object north or south of the celestial equator. It is measured in degrees, minutes, and seconds, and is always positive for objects north of the equator and negative for objects south of the equator.
The right ascension is the angular distance of a celestial object east of the vernal equinox. It is measured in hours, minutes, and seconds, and is always positive for objects east of the vernal equinox and negative for objects west of the vernal equinox.
The declination and right ascension system is used by astronomers to track the movement of objects in the sky. It is also used by amateur astronomers to identify objects in the night sky.
The altitude and azimuth system is a coordinate system that is used to specify the position of an object in the sky relative to the observer. The altitude is the angle between the object and the horizon, and the azimuth is the angle between the object and the north point on the horizon.
The altitude and azimuth system is not as convenient as the declination and right ascension system because it cannot be used to specify the position of objects that are not visible from the observer’s location.
The declination and hour angle system is a coordinate system that is used to specify the position of an object in the sky relative to the observer’s meridian. The declination is the angle between the object and the celestial equator, and the hour angle is the angle between the object and the observer’s meridian.
The declination and hour angle system is not as convenient as the declination and right ascension system because it is not a spherical coordinate system. This means that it cannot be used to specify the position of objects that are not visible from the observer’s location.