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disc dial: type of sundial belonging in the class of altitude dial.
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dividers: instrument with jointed legs for measuring and transferring distances, see article on the dividers.
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dominical letter: letter denoting the day of the first Sunday of the year, see article on time and date.
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drawing instruments: instruments used for drawing and constructing geometrical figures, see article on drawing instruments.
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Easter table: table for calculating the date of Easter, see article on time and date.
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ecliptic: line on the celestial sphere representing the annual path of the sun through the stars.
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epacts: numbers used in the calculation of Easter, see article on time and date.
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equal hours: system of hour reckoning, see article on time and date.
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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.
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equatorial: relating to or based on the equator. Has much the same meaning as equinoctial.
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equatorial dial: another name for equinoctial dial.
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equatorium: instrument to determine the longitude of one or more of the planets at any given time.
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equinoctial: relating to or based on the equator, or relating to the equinox.
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equinoctial dial: sundial where the hour plate or circle is set parallel to the equator, see article on the sundial.
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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.
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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.
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folding rule: see rule.
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folding rule and level: a compound instrument combining the functions of both a folding rule and level.
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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.
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geographical astrolabe: form of astrolabe, where the lower plate is projected for the earth, while the rete includes the ecliptic.
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