Astronomical sector, 16th-century artwork. This device was used to make accurate observations of the position of an object in the sky, such as a star or the Sun. The sight (lower left) would be used to line up the hinged rulers (right) with the object being observed. The position of the star was recorded as an angle from the vertical or horizontal, as read from the curved area (left). Artwork from 'The making and use of the geometricall instrument, called a sector' (1598) by Thomas Hood.
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