The luminaries were what traditional astrologers called the two astrological "planets" which were the brightest and most important objects in the heavens, that is, the Sun and the Moon. Luminary means, source of light. The sun and moon, being the most abundant sources of light to the inhabitants of Earth are known as luminaries. The astrological significance warrants the classification of the Sun and Moon separately from the planets, in that the Sun and Moon have to do with Man's spiritual consciousness, while the planetary influences operate through the physical mechanism. The Moon is a luminary in the biblical sense that it affords to Man "light by night". Some early, Pre-Newtonian astronomers to observe and study luminaries include Pythagoras, Aristotle, Claudius Ptolemy, al-Khwarizmi, Nicolaus Copernicus, Tycho Brahe, Galileo Galilei, and Johannes Kepler.
The Sun and Moon were considered the rulers of day, and night, in accordance with the doctrine of astrology of sect: diurnal (or daytime) planets, which were ruled by the Sun, and nocturnal (or nighttime) planets, which were ruled by the Moon.
The Sun was also the sect ruler—or the luminary of sect for all charts of events and individuals born in the daytime, when the Sun was over the horizon; and the Moon was the sect ruler or luminary of sect for night charts, when the Sun was below the horizon.
Ancient astrologers divided all astrological factors into day and night groups: essential dignities, Arabian Parts (or "Lots") and all planetary characteristics. Even each of the Starry planets themselves "belonged" to one luminary or the other. The luminary "in charge" of any given chart was called the luminary of sect. (See sect.)