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lunar volvelle: volvelle indicating the age of the moon, which typically converts between the time indicated by the shadow of the moon on a sundial and solar time.
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magic square: square grid with a number in each cell for which the sum of each row, column and diagonal is the same.
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magnetic compass: instrument indicating directions by a magnetic needle, see article on the compass.
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magnetic deviation: the angle between geographical north and the direction indicated by a compass needle.
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magnitudes: numbers in a scale of the relative brightnesses of the stars, 1 being the brightest.
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mariner's astrolabe: altitude-measuring instrument for finding latitude at sea, having a heavy brass or bronze ring, suspended by a shackle and ring, with a degree scale and a centrally-pivoted alidade.
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mater: part of an astrolabe, see article on the astrolabe.
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mathematical compendium: compound instrument for performing various functions in practical mathematics.
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mathematical instruments: collections of instruments of assorted kinds for performing functions in practical mathematics.
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measuring rod: an instrument used to measure distances or depths. See also gauging rod.
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measuring rods: see measuring rod.
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meridian: the plane containing the observer and both celestial poles, or containing the observer, the zenith and the pole, or, more colloquially, the north-south line at a particular position on the earth.
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meridian circle: circular scale of degrees which in use is aligned with the meridian.
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mining instruments: in this period mining instruments were principally for surveying, adapted for the special conditions of working underground in mines.
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nautical circle: generic term for a circular mathematical instrument of use in navigation, but likely to carry a range of mathematical and astronomical scales.
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nautical hemisphere: a combination of graduated arcs and circles used for navigational calculations, see article on the nautical hemisphere.
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navicula dial: type of altitude dial in the shape of a ship.
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nocturnal: instrument for finding the time at night from the orientation of the stars, see article on the nocturnal.
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nocturnal and quadrant: compound instrument which combines both the functions of a nocturnal and quadrant, usually on two different sides of the same instrument, with equal importance given to each.
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nocturnal and sundial: compound instrument which combines both the functions of a nocturnal and sundial, usually on two different sides of the same instrument, with equal importance given to each.
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nonius: a way of subdividing a quadrant of a circle to provide fine discrimination of parts of degrees, comparable in purpose to the later vernier scale. The name comes from the latinized surname of the 16th-century Portuguese mathematician Pedro Nu?ez.
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Nuremberg hours: system of hour reckoning, see article on time and date.
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octant: the eighth part of a circle or an instrument measuring up to 45 degrees.
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old quadrant: type of horary quadrant, see article on the quadrant.
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opposition: two planets 180? from each other in the ecliptic are said to be in opposition. This relative position had important astrological significance.
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ordinary hours: system of hour reckoning, see article on time and date.
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orthographic planisphere: flat map produced by orthographic projection.
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pedometer: device worn by a walker to measure distance by counting paces.
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pendant sundial: a form of sundial suspended by a cord and possibly hung around the neck.
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perpetual calendar: calendar covering a number of years, see article on time and date.
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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.
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pillar dial: type of altitude dial, see article on the sundial.
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pin gnomon: the part of a sundial which casts the shadow, where this part is in the form of a pin.
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plane table: type of surveying instrument, see article on the plane table.
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plane table alidade: an alidade specially adapted for use with a plane table.
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planetary hours: system of hour reckoning, see article on time and date.
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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.
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planisphere: a representation of a spherical body on a flat surface, commonly a map of the earth or of the heavens.
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