Ptolemy

• Claudius Ptolemaeus (c.90-c.168 CE), known as Ptolemy, was a Greco-Roman Geographer, Mathematician, Astronomer and Astrologer who lived and worked in Alexandria, Egypt.
• He is best known for his Geographia, a Map of the World, and the Almagest, a listing of all the Stars and Constellations.

Works

• Ptolemy's Geographia
  • a Geography of the known World.
• Ptolemy's Almagest
  • an astronomical Work based on a Geocentric Universe.
  • Ptolemy states that Hipparchus was his source for calculating the Mean Synodic Month.
• Ptolemy's Tetrabiblos
  • or ‘Quadripartitum’ meaning ‘the four books’, is an Astrological Work combining Astrology with Philosophy of Aristotle.
• Ptolemy's Planisphaerium
  • a description of the mathematical calculations needed to project the stars on to the celestial sphere. This appears to be a guide to constructing an Astrolabe, but there is no proof that he built one, although he did build an Armillary Sphere.
• ‘Optics’
  • a Work describing the Reflection, Refraction and Colour of Light. It contains a Table giving the angle of refraction of light from air to water.

Other Contemporary Astronomers

• Zhang Heng (78-139 CE) Chinese Astronomer.