I have problems to understand the point of "mean sun" and "true sun". As I understood the mean sun is set in the center of the earth orbit (which is a circle). So Ptolemy, Copernicus and Brahe used the "mean sun", however they knew that this isn't the real position of the sun? Did they do that due to the reason it would fit with the mars oppositions?*
(*Three of them used circles to describe orbits of planets. But if they want to link that together with the observations it wouldn't fit.)
Is that right? So even Ptolemy knew that the sun isn't in the middle of the orbit of the earth?
Here is a website which I think describes it: http://science.larouchepac.com/kepler/newastronomy/part1/5/index.html http://science.larouchepac.com/kepler/newastronomy/part1/6/index.html
Due to my first language is not English it might be possible that I didn't understand some important aspects of the given links.