hello, Im solving a problem about the angular velocity in an elliptic keppler orbit as seen from the empty focus of the ellipse. 1. The problem statement, all variables and given/known data Show that the angular motion of a keppler orbit as seen from the empty focus is uniform to first order in the eccentricit. 3. The attempt at a solution I have tried various ways to attack this problem but they all run into the same type of problem. What Im trying to get is a way to relate the constant angular momentum around the non-empty focus to the angular motion as seen from the empty focus. But all such attempts get into very complicated calculations, if not impossible. Does anyone have a good way to relate these two angular motions to each other? any ideas of how to adress the problem to make it simpler? or any references where I could find something helpfull...? I would appreciate it!