Determination of the Sun's orbit. Hipparchus, Ptolemy, al-Battānī, Copernicus, Tycho Brahe (Q1389834)

This is an outstanding paper that obviously has required a lengthy effort. It is excellently developed and presents a set of really interesting results. The paper analyzes the solar elements of several historical records from astronomers like Hipparchus, Ptolemy, al-Battānī, Copernicus and Tycho Brahe and their theoretical deviations. The basic conditions under which Tycho's observations were made are clarified and applied to other astronomers' observations. The results of the observations depend on the special circumstances under which they were made. Those who neglected the erroneous traditional solar parallax (like al-Battānī and Copernicus) determined the sun's orbit accurately within the effect of refraction. But the effect of Tycho's erroneous solar parallax values, on the measures of the time intervals and on the solar position, turned out to be double in the length of the half-year between two equinoxes, whereas it disappeared in the length of the tropical year. The problem of parallax and refraction were, finally, the main obstacle faced by Kepler in his Astronomia Nova.