Does anyone know where I can obtain English translations of Ptolemy's
"Analemma" and "Planisphaerium?" Translations of his better known works are
readily available.
BTW, an online version of Vitruvius' "Architecture" is available at the link
below, where Book 9 discusses sundial contruction.
http://www.ukans.edu/history/index/europe/ancient_rome/E/Roman/Texts/Vitruvi
us/9.html
thanks, Tom
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ENCYCLOPÆDIA BRITANNICA
Ptolemy - Work in mathematics and geography.
As a geometrician of the first order, Ptolemy performed important work in
mathematics. He devised new geometrical proofs and theorems; and, in a book
entitled Analemma (Greek Peri analemmatos; Latin De analemmate), he
discussed the details of the projection of points on the celestial sphere
(an imaginary sphere extending outward from the Earth for an infinite
distance and on whose surface the objects in space appear to be located)
onto three planes at right angles (90º) to each other--the horizon, the
meridian, and the prime vertical. In another book, the Planisphaerium,
Ptolemy is concerned with stereographic projection--the delineation of the
forms of solid bodies on a plane--and here he used the south celestial pole
as his centre of projection.
