what kind of researches had he carried out?
He estimated the Sun was at an average distance of 1,210 Earth radii.
Ptolemy
His "Planetary Hypotheses" went beyond the mathematical model of the "Almagest" to present a physical realization of the universe as a set of nested spheres, in which he used the epicycles of his planetary model to compute the dimensions of the universe. He estimated the Sun was at an average distance of 1,210 Earth radii, while the radius of the sphere of the fixed stars was 20,000 times the radius of the Earth.
what is serpens? A constellation of the northern hemisphere. who discovered it? Ptolemy. who was he? A mathematician, astronomer and astrologer.
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Ptolemy [SEP] Astronomy
Ptolemy's model, like those of his predecessors, was geocentric and was almost universally accepted until the appearance of simpler heliocentric models during the scientific revolution. His "Planetary Hypotheses" went beyond the mathematical model of the "Almagest" to present a physical realization of the universe as a set of nested spheres, in which he used the epicycles of his planetary model to compute the dimensions of the universe. He estimated the Sun was at an average distance of 1,210 Earth radii, while the radius of the sphere of the fixed stars was 20,000 times the radius of the Earth. Ptolemy presented a useful tool for astronomical calculations in his "Handy Tables", which tabulated all the data needed to compute the positions of the Sun, Moon and planets, the rising and setting of the stars, and eclipses of the Sun and Moon.