Lecture 4.3  Hipparchus and Ptolemy

Autolykus of Pitane on risings and settings
    heliacal rising: first sighting in E before dawn
    heliacal setting: last sighting in W after dusk
   
Aristarchus – first half 200s:
    famous as the ancient Copernicus
        heliocentric model of the cosmos and
    surviving treatise on relative distance of moon and sun
    for this see Lindberg
    angle at the half moon (Aristarchus said 87 degrees, actually 89;52)
    sun is between 18 and 20 x the distance of the moon from the earth

Apollonius of Perga  (200BCE)  originated the epicycle theory as qualitative explanation
    explain the solar anomaly
    demonstrated equality of epicycle and eccentric theory

Hipparchus: precession of the equinox;
    diopter (instrument for star citing); celestial projections for early astrolabe
    precession is by the gravitation of the sun and the moon on the bulge of the earth's equitorial region
    as a result our pole star (now 1 degree from N, was in Hipparchus' time 150 BC 12, 24'

Ptolemy (A.D. 140): Almagest (Syntaxis) a compendium of astronomical mathematical theory
    makes use of epicycles and deferents to explain the varying motions of the planets
    also used equant system, which we did not cover in class

we studied the solar anomaly due to the elliptical orbit of the earth around the sun and considered how Ptolemy mapped that motion onto the deferent and epicycle system
    for the sun one revolution of the epicycle for one revolution around the deferent
    accounted for perigee (our perihelion) and apogee (our apohelion)
    accounted for the difference in speed of the sun from west to east on the ecliptic

 

Ptolemy