Level horizontal sundial (Eudoxus’ “Arachne” and “Pelekinos” of Patrokles)

Kostas Kotsanas

A grid with 11 engraved hour lines and three curves indicated, with the help of the shadow trace from the vertical gnomon edge (oriented to the South) 10 out of the 12 unequal (depending on the season) day hours. The closest curve to the gnomon indicated the course of the Sun’s shadow at the summer solstice, the most distant at the winter solstice and the middle one (straight line) at the equinoxes. The entire line grid was named “Analemma” and sometimes it included 4 more curves that defined the Sun shade’s orbit for the entry of the remaining zodiacs (months). Later on, an oblique gnomon was used with inclination equal to the latitude of the place (φ) so that only the orientation of its shadow for the indication of the hours was enough.