Level horizontal sundials
(the spider’s web of Eudoxus and the“pelekinos”
of Patrokles)

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 shade’s orbit of the Sun for the entry of the remaining zodiacs (months). Later an oblique gnomon was used with inclination equal to the latitude of the place (φ) so that only the orientation of the shadow for the indication of the hours was enough.

 


 

Category
Level sundials