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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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