Luna (goddess) as Juno Covella, Juno of the crescent moon. Both Juno and Diana were invoked as childbirth goddesses with the epithet "Lucina". Luna is often depicted driving a two-yoke chariot called a "biga", drawn by horses or oxen. In Roman art, the charioteer Luna is regularly paired with the Sun driving a four-horse chariot ("quadriga"). Isidore of Seville explains that the "quadriga" represents the sun's course through the four seasons, while the "biga" represents the moon, "because it travels on a twin course with the sun, or because it is visible both by day and by night—for they yoke together one
Celestial sphere the equatorial coordinate system, the celestial equator divides the celestial sphere into two halves: the northern and southern celestial hemispheres. Because astronomical objects are at such remote distances, casual observation of the sky offers no information on their actual distances. All celestial objects seem equally far away, as if fixed onto the inside of a sphere with a large but unknown radius, which appears to rotate westward overhead; meanwhile, Earth underfoot seems to remain still. For purposes of spherical astronomy, which is concerned only with the directions to celestial objects, it makes no difference if this is actually the case