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unequal hours: system of hour reckoning, see article on time and date.
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universal dial: a sundial that can be used in any latitude.
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universal projection: a type of projection of the celestial sphere appropriate for use in any latitude.
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vane: upright piece, in this context usually forming a sight and often pierced with a pinhole, a slit, or a slot with a vertical wire.
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vertical dial: sundial where the hour lines are marked on a vertical surface, see article on the sundial.
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vertical disc dial: sundial where the hour lines are marked on a vertical surface in the form of a disc, see article on the sundial.
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volvelle: a device which rotates; usually referring to one or more discs which turn within a circular scale.
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wedge: the part of an astrolabe which secures the pin; also called the 'horse'.
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wegweiser: a circle marked with the points of the compass and a rotating index.
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wind names: a nomenclature for dividing an azimuth circle into degrees, where eight 45-degree scales are allocated to eight traditional named winds of the Mediterranean.
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wind rose: type of compass rose, where the directions are indicated by the names or initials of the traditional winds of the Mediterranean. May also refer to a whole instrument serving only to indicate the names of the wind directions.
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