The Kepler Equation, M = E- e Sin E

The Kepler equatio M = E- e Sin E can be used to compute planetary longitudes.

M is the Mean Anomaly of the planet and E, the Eccentric Anomaly. Eccentric Anomaly is an auxiliary angle used in Kepler's Equations.

e is Eccentricity of Orbit. The planet's orbit is elliptical and not circular and Eccentricity or e is always Zero at Circle, 0-1 at ellipse and one at Parabola !

The Kepler Equation can be put in a different way

E = M + e Sin E