Figure 15: Nicolaus Copernicus, Feb. 19, 1473 - May 24, 1543 Born Torun, Poland, died Frauenburg, Poland.
It was about 1530 that Copernicus arrived at his model of the Sun-centered (heliocentric) universe.
Almost 1500 years had elapsed since Ptolemy. Is this problem so difficult or did something intervene that was more important than astronomy? Well, something intervened. it is called the dark ages. After the time of Ptolemy, came a series of oppressive rulers, restrictive societies and mystic belief systems where science, freedom and honest government were essentially nonexistent. It is estimated that the discoveries of science were delayed by a thousand years because dominant world societies took the path greed and competition for power. If they hadn't, we might be visiting the planets and stars in the year 2000 rather than studying about them from a book. (That last paragraph is my view.)
Copernicus correctly identified the ordering of the planets known then.
Initially, he thought that each of the planets moved in a perfect circle around the Sun. That immediately explained an enormous number of things, but subsequent careful checking showed that their were differences between predictions of times and places and the actual occurrences.