The daily, or diurnal, westward paths of stars are circles that are centered on the north celestial pole. The diurnal circles grow smaller for stars that are nearer the north celestial pole. The celestial equator is a line on the celestial sphere that divides it into northern and southern hemispheres.
The equatorial system is used to locate stars on the celestial sphere. This system resembles the terrestrial system of longitude and latitude. In the equatorial system, declination describes the angular distance of a star north or south of the celestial equator. Right ascension describes the east-west location of a star on the celestial sphere.
The Sun appears to move eastward among the stars on a path called the ecliptic, and its motion is repeated annually. The ecliptic is inclined with respect to the celestial equator, so the declination of the Sun varies during the year.
Changes in the declination of the Sun produce an annual pattern of change in its rising and setting points as well as change in its altitude at noon. These changes are responsible for the seasons.
Apparent solar time is reckoned by the position of the Sun in the sky. The variable rate of the Sun's motion on the ecliptic causes changes in the length of the solar day throughout the year.
The phases of the Moon happen because the part of the Moon's illuminated hemisphere that we see varies throughout a synodic month.
The Moon appears to move eastward among the stars, returning to the same place after a sidereal month.
The planets usually appear to move eastward among the stars. However, at regular intervals they appear to move westward during periods of retrograde motion. The motions of the planets among the stars are quite complex.
