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hodometer: device for measuring distance by means of a wheel, pushed along the ground, attached to a geared movement with a dial or other form of distance register.
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horary quadrant: quadrant used to tell the time, usually from a measure of solar altitude, see article on the quadrant.
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horizon obliquus: line denoting the local horizon on an astrolabe latitude plate, see article on the astrolabe.
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horizon rectus: east-west line on an astrolabe latitude plate, see article on the astrolabe.
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horizontal dial: sundial where the hour lines are marked on a horizontal surface, see article on the sundial.
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hour lines: the time divisions on a sundial or other astronomical instrument.
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hour ring: the part of a sundial marked with the time divisions, where this part is in the form of a ring or broken ring.
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inclining dial: type of sundial projected as a horizontal dial for a particular latitude, but which can be inclined for use in a range of other latitudes.
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Italian hours: system of hour reckoning, see article on time and date.
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Jacob's staff: name for a cross-staff, especially when used for surveying, see article on the cross-staff.
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Julian calendar: calendar introduced by Julius Caesar and used in Europe until the sixteenth century, or later, see article on time and date.
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latitude: angle above or below the equator to indicate position on the earth. The celestial latitude, however, is an angular distance with respect to the ecliptic.
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latitude plate: part of an astrolabe with a projection of altitude and azimuth lines on to the equatorial plane, see article on the astrolabe.
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latitude projections: projection of altitude and azimuth lines on to the equatorial plane, see article on the astrolabe.
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level: name for different types of instrument used in surveying for determining the horizontal direction and differences in height, and in gunnery and elsewhere for adjusting something to the horizontal. See also gunner's level.
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level and sight: instrument used to set a large gun to the horizontal, or to elevate and aim it on a target, see article on the gunner's sight and level.
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limb: the outermost part or edge of a circular or part-circular instrument carrying a scale, usually divided in degrees.
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longitude: angle parallel to the equator to indicate position on the earth. The celestial longitude, however, is an angular distance parallel to the ecliptic.
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lunar dial: dial where the shadow is cast by moonlight instead of sunlight, see article on the sundial.
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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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