Not an historian or astronomer but I guess Copernicus' main work is about heliocentrism, but it uses epicycles. It has to because in his views planets made cir

Not an historian or astronomer but I guess Copernicus' main work is about heliocentrism, but it uses epicycles. It has to because in his views planets made circles around the sun and at constant speed. Indeed Copernicus was aware this only could not explain what is observed so he had to introduce epicycles as in Hipparchian, Ptolemaic system. Circles with epicycles are just an approximation for ellipses, but ellipses could not be introduced without a theory of gravity.