That should link to a capx demonstrating. t is the step, or speed, theta is angle of rotation, a is one axis of the ellipse, b is the other
The initial transformation I posted rotates about the origin, so this new one is corrected for that.
The parametric equation is:
X(t) = Xc + a * cos(t) * cos(theta) - b * sin(t) * sin(theta)
Y(t) = Yc + a * cos(t) * sin(theta) + b *sin(t) * cos(theta)
AND OMG I NEED TO REFRESH MY TRIG. Thanks for pointing out a glaring weakness of mine. :(