Conical sundial (Dionysiodoros' cone)

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Conical sundial (Dionysiodoros' cone)


11 hour lines engraved on a semi conical concave surface with a slope towards the celestial pole, arranged at distances of 15 degrees define the 12 daily hours, while the three curves define the course of the sun during the summer solstice (the lowest line) the equinoxes (the central line) and the winter solstice (the upper line). On other days, the shadow of the sun outlines parallel arcs between the curves, according to the season.