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109 to 158 of 227 glossary terms
longitude: angle parallel to the equator to indicate position on the earth. The celestial longitude, however, is an angular distance parallel to the ecliptic.
lunar dial: dial where the shadow is cast by moonlight instead of sunlight, see article on the sundial.
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.
magic square: square grid with a number in each cell for which the sum of each row, column and diagonal is the same.
magnetic compass: instrument indicating directions by a magnetic needle, see article on the compass.
magnetic deviation: the angle between geographical north and the direction indicated by a compass needle.
magnitudes: numbers in a scale of the relative brightnesses of the stars, 1 being the brightest.
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.
mater: part of an astrolabe, see article on the astrolabe.
mathematical compendium: compound instrument for performing various functions in practical mathematics.
mathematical instruments: collections of instruments of assorted kinds for performing functions in practical mathematics.
measuring rod: an instrument used to measure distances or depths. See also gauging rod.
measuring rods: see measuring rod.
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.
meridian circle: circular scale of degrees which in use is aligned with the meridian.
mining instruments: in this period mining instruments were principally for surveying, adapted for the special conditions of working underground in mines.
nautical circle: generic term for a circular mathematical instrument of use in navigation, but likely to carry a range of mathematical and astronomical scales.
nautical hemisphere: a combination of graduated arcs and circles used for navigational calculations, see article on the nautical hemisphere.
navicula dial: type of altitude dial in the shape of a ship.
nocturnal: instrument for finding the time at night from the orientation of the stars, see article on the nocturnal.
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.
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.
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.
Nuremberg hours: system of hour reckoning, see article on time and date.
octant: the eighth part of a circle or an instrument measuring up to 45 degrees.
old quadrant: type of horary quadrant, see article on the quadrant.
opposition: two planets 180? from each other in the ecliptic are said to be in opposition. This relative position had important astrological significance.
ordinary hours: system of hour reckoning, see article on time and date.
orthographic planisphere: flat map produced by orthographic projection.
pedometer: device worn by a walker to measure distance by counting paces.
pendant sundial: a form of sundial suspended by a cord and possibly hung around the neck.
perpetual calendar: calendar covering a number of years, see article on time and date.
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.
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.
polyhedral dial: sundial with hour lines on various faces of a solid figure, see article on the sundial.
prime vertical: celestial great circle passing through the east and west points and the zenith.
primum mobile: instrument for finding the sines and versed signs of angles, see article on the primum mobile.
projection: translation of a figure on to a plane or curved surface using straight lines in a systematic way. For example, a spherical surface can be projected on to a plane (the plane of projection) by means of straight lines drawn from all points on the surface to a certain defined point (the point of projection) and marking where they intersect the plane. In a stereographic projection, such as is used for the ordinary astrolabe, points on a containing circle are projected on to an equatorial plane from one pole; in an orthographic projection, such as is used in a Rojas design of universal astrolabe, the point of projection is at infinity and the projection lines are parallel.
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