|phase of the moon: the changing appearance of the moon throughout its approximately monthly cycle, from the thin crescent of new moon to the complete circle of full moon and back again.
|pillar dial: type of altitude dial, see article on the sundial.
|pin gnomon: the part of a sundial which casts the shadow, where this part is in the form of a pin.
|plane table: type of surveying instrument, see article on the plane table.
|plane table alidade: an alidade specially adapted for use with a plane table.
|planetary hours: system of hour reckoning, see article on time and date.
|planetary temperaments: astrological character of the fixed stars; as assigned in classical astrology, each star had a nature and effect similar to one or more of the planets.
|planisphere: a representation of a spherical body on a flat surface, commonly a map of the earth or of the heavens.
|planispheric astrolabe: astronomical instrument based on a planispheric projection of the heavens, see article on the astrolabe.
|plate: part of an astrolabe with a projection of altitude and azimuth lines on to the equatorial plane, see article on the astrolabe.