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For the Moon, Ptolemy began with Hipparchus' epicycle-on-deferent, then added a device that historians of astronomy refer to as a "crank mechanism": [30] he succeeded in creating models for the other planets, where Hipparchus had failed, by introducing a third device called the equant. Ptolemy wrote the Syntaxis as a textbook of mathematical ...
Ptolemy's Handy Tables (Ancient Greek: πρόχειροι κανόνες, romanized: Procheiroi kanones) is a collection of astronomical tables that second century astronomer Ptolemy created after finishing the Almagest. The Handy Tables elaborated the astronomical tables of the Almagest and included usage instructions, but left out the ...
Ptolemy states that having dealt with the former subject (astronomy) in its own treatise, he "shall now give an account of the second and less self-sufficient method in a properly philosophical way, so that one whose aim is the truth might never compare its perceptions with the sureness of the first". [27]
The table of chords, created by the Greek astronomer, geometer, and geographer Ptolemy in Egypt during the 2nd century AD, is a trigonometric table in Book I, chapter 11 of Ptolemy's Almagest, [1] a treatise on mathematical astronomy. It is essentially equivalent to a table of values of the sine function.
Ancient and medieval thinkers, however, considered the celestial orbs to be thick spheres of rarefied matter nested one within the other, each one in complete contact with the sphere above it and the sphere below. [2] When scholars applied Ptolemy's epicycles, they presumed that each planetary sphere was exactly thick enough to accommodate them ...
Originating from the Thebaid region of Upper Egypt, he worked at Alexandria and wrote works on astronomy including the Almagest, the Planetary Hypotheses, and the Tetrabiblos, as well as the Handy Tables, the Canobic Inscription, and other works unrelated to astronomy. Ptolemy's Almagest (originally titled The Mathematical Syntaxis) is one of ...
The Planisphaerium is a work by Ptolemy. The title can be translated as "celestial plane" or "star chart". In this work Ptolemy explored the mathematics of mapping figures inscribed in the celestial sphere onto a plane by what is now known as stereographic projection. This method of projection preserves the properties of circles.
The triquetrum (derived from the Latin tri-["three"] and quetrum ["cornered"]) was the medieval name for an ancient astronomical instrument first described by Ptolemy (c. 90 – c. 168) in the Almagest (V. 12). Also known as Parallactic Rulers, it was used for determining altitudes of heavenly bodies.