how different is his planetary model from the conventional one?
It was geocentric and was almost universally accepted until the appearance of simpler heliocentric models during the scientific revolution.
Ptolemy
 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.

what is serpens? A constellation of the northern hemisphere. who discovered it? Ptolemy. who was he? A mathematician, astronomer and astrologer. what kind of researches had he carried out? He estimated the Sun was at an average distance of 1,210 Earth radii. has his researches been published ? Yes, "Almagest". how is he associated with music? He wrote "Harmonics", on music theory. what is the former research work based on ? The apparent motions of the stars and planetary paths. when was it published? 2nd-century.
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Ptolemy [SEP] Astronomy
Ptolemy's "Handy Tables" provided the model for later astronomical tables or "zījes". In the "Phaseis" ("Risings of the Fixed Stars"), Ptolemy gave a "parapegma", a star calendar or almanac, based on the appearances and disappearances of stars over the course of the solar year.