What is the version of the following sentence with correct punctuation?

Based on his observations of solstices and equinoxes Ptolemy found the lengths of the seasons and based on these he proposed a simple model for the sun which was a circular motion of uniform angular velocity but the earth was not at the centre of the circle but at a distance called the eccentricity from this centre
Based on his observations of solstices and equinoxes, Ptolemy found the lengths of the seasons and, based on these, he proposed a simple model for the sun which was a circular motion of uniform angular velocity, but the earth was not at the centre of the circle but at a distance called the eccentricity from this centre.