|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.
|plumb level: device for determining a horizontal level or an angle of elevation by a plumb line or plummet.
|plumb line: a suspended thread with a weight at its end, indicating the vertical.
|plummet: a form of plumb line in which the 'line' and weight are a single rigid piece.
|polar dial: type of sundial, see article on the sundial.