Sundial
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A sundial is a horological device that tells the time of day when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat plate
SSW facing, vertical declining sundial on the Moot Hall in Aldeburgh, Suffolk, England. The gnomon is a rod that is very narrow, so it functions as the style. The Latin motto loosely translates as "I only count the sunny hours."
A horizontal dial commissioned in 1862, the gnomon is the triangular blade. The style is its inclined edge.
Bowstring sundial in Singapore Botanic Gardens. The design shows that Singapore is located almost at the equator.
World's oldest sundial, from Egypt's Valley of the Kings (c. 1500 BC)
Celestial sphere
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In astronomy and navigation, the celestial sphere is an abstract sphere that has an arbitrarily large radius and is concentric to Earth. All objects in the sky can be conceived as being projected upon
Celestial globe by Jost Bürgi (1594)
