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 Glossary
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 conjunction: two planets having the same position (in longitude) in the ecliptic are said to be in conjunction. This relative position had important astrological significance. cross-staff: instrument for measuring angles between distant objects, mostly altitudes, see article on cross-staff. cross-staffs: see article on cross-staff crucifix dial: form of polyhedral sundial in the shape of a crucifix, see article on sundial. cylinder dial: type of altitude dial, see article on the sundial. declination: angle above or below the celestial equator. declinatory: instrument used in constructing a sundial, to find the declination of a plane. degrees: the conventional divisions of a circle, one being the 360th part of a circle, and thus the units used to measure and express angles. diagonals: lines used in the subdivision of divisions of an arc, also known as transversals. Each diagonal line is drawn across the division from its beginning to its end, and is divided linearly either by dots or by concentric arcs. In this way the linear division of a line can be used for the angular subdivision of an arc. dial: instrument for telling time by the position of the sun (occasionally by the moon), see article on the sundial. dialling quadrant: instrument in the form of a quadrant used in the construction of a sundial. diptych dial: type of sundial which, in many cases, could be called an astronomical compendium, in the form of a folding tablet, usually in ivory, with at least a string gnomon and a horizontal dial on the inside, but often with other dials as well. disc dial: type of sundial belonging in the class of altitude dial. dividers: instrument with jointed legs for measuring and transferring distances, see article on the dividers. dominical letter: letter denoting the day of the first Sunday of the year, see article on time and date. drawing instruments: instruments used for drawing and constructing geometrical figures, see article on drawing instruments. Easter table: table for calculating the date of Easter, see article on time and date. ecliptic: line on the celestial sphere representing the annual path of the sun through the stars. epacts: numbers used in the calculation of Easter, see article on time and date. equal hours: system of hour reckoning, see article on time and date. equator: circle on the earth's surface 90 degrees from the poles, or the circle on the celestial sphere 90 degrees from the celestial poles. equatorial: relating to or based on the equator. Has much the same meaning as equinoctial. equatorial dial: another name for equinoctial dial. equatorium: instrument to determine the longitude of one or more of the planets at any given time. equinoctial: relating to or based on the equator, or relating to the equinox. equinoctial dial: sundial where the hour plate or circle is set parallel to the equator, see article on the sundial. equinoctial ring dial: type of sundial, included as an equinoctial dial, comprising two pivoted rings and a bridge for adjusting for solar declination, or of three rings. equinox: either of two points on the celestial sphere where the equator meets the ecliptic, representing the position of the sun when it is 90 degrees from the poles, or the two dates in the year when the sun is in this position in its annual cycle. folding rule: see rule. folding rule and level: a compound instrument combining the functions of both a folding rule and level. gauging rod: measuring stick, usually with a scale to provide a direct reading of volume, such as the liquid content of a barrel, or the weight of a cannonball. geographical astrolabe: form of astrolabe, where the lower plate is projected for the earth, while the rete includes the ecliptic. geographical planisphere: map of the earth, produced by geometrical projection of a sphere on to a flat surface. Included as the more prominent part of the geographical astrolabe. geometrical square: form of quadrant, with sides divided equally and having an alidade at one corner, used for measuring angles in terms of ratios in the manner of a shadow square on the back of an astrolabe. globe dial: form of sundial, where the hour lines are on the outer surface of a sphere. gnomon: the part of a sundial that casts the shadow for indicating the time. golden numbers: numbers denoting the positions of years in the lunar cycle, see article on time and date. graphometer: type of surveying instrument, see article on the graphometer. gunner's caliper: a instrument used to take dimensions in gunnery, such as the diameter of cannons and projectiles. gunner's compendium: an instrument combining several functions required by the gunner, often incorporating the gunner's sight and gunner's level, along with additional elements. gunner's folding rule: a folding rule carrying tables or scales specially adapted for the use of gunners. gunner's gauge scales: scales which provide the weight of a sphere (the shot) from a measurement of its diameter; in gunnery these scales were traditionally provided for iron, lead and stone. gunner's level: instrument used to set the elevation of a large gun, see article on the gunner's sight and level. gunner's rule: see rule. gunner's sight: instrument used to elevate and aim a large gun, see article on the gunner's sight and level. gunner's sight and level: 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. gunnery instrument: see gunner's compendium. 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. horary quadrant: quadrant used to tell the time, usually from a measure of solar altitude, see article on the quadrant. horizon obliquus: line denoting the local horizon on an astrolabe latitude plate, see article on the astrolabe. horizon rectus: east-west line on an astrolabe latitude plate, see article on the astrolabe. horizontal dial: sundial where the hour lines are marked on a horizontal surface, see article on the sundial. hour lines: the time divisions on a sundial or other astronomical instrument. 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. 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. Italian hours: system of hour reckoning, see article on time and date. Jacob's staff: name for a cross-staff, especially when used for surveying, see article on the cross-staff. Julian calendar: calendar introduced by Julius Caesar and used in Europe until the sixteenth century, or later, see article on time and date. 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. latitude plate: part of an astrolabe with a projection of altitude and azimuth lines on to the equatorial plane, see article on the astrolabe. latitude projections: projection of altitude and azimuth lines on to the equatorial plane, see article on the astrolabe. 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. 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. limb: the outermost part or edge of a circular or part-circular instrument carrying a scale, usually divided in degrees. 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.
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