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* Book I contains an outline of [[Aristotle]]'s cosmology: on the spherical form of the heavens, with the spherical Earth lying motionless as the center, with the [[fixed stars]] and the various [[planets]] revolving around the Earth. Then follows an explanation of [[chord (geometry)|chords]] with [[Ptolemy's table of chords|table of chords]]; observations of the obliquity of the [[ecliptic]] (the apparent path of the Sun through the stars); and an introduction to [[spherical trigonometry]].
* Book II covers problems associated with the daily motion attributed to the heavens, namely risings and settings of celestial objects, the length of daylight, the determination of [[latitude]], the points at which the [[Sun]] is vertical, the shadows of the [[gnomon]] at the [[equinox]]es and [[solstice]]s, and other observations that change with the
* Book III covers the length of the year, and the motion of the [[Sun]]. Ptolemy explains [[Hipparchus]]' discovery of the [[Precession (astronomy)|precession]] of the equinoxes and begins explaining the theory of [[epicycles]].
* Books IV and V cover the motion of the [[Moon]], lunar [[parallax]], the motion of the lunar [[apogee]], and the sizes and distances of the Sun and Moon relative to the Earth.
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