In Cairo citadel, in front of Muhammad-Ali mosque, on a tower wall, there is a sundial which works very well. This sundial is certainly an exceptional one because of its furnitures, signs and also complexity of calculations which used for its design and structure (a cylindrical, with south-western inclination and four polar gnomons) and can be counted as an excellent evidence for Muslims extraordinary technical progress in making gnomons and sundials in 18th century.
This article, for the first time, provides a consideration on this sundial relying on the bases of modern mathematics
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