Ab initio Calculation of Galactic Rotation Curves in vacuo

Galactic rotation curves appear to become asymptotically flat far from the core, a feature that can be explained with an optical model of gravitational forces. With the core as a central lens, gravity from one side of the galaxy can be focused by the core onto the oposite side, thereby increasing radial forces, above those expected from a central Newtonian model. Using basic optics, the asymptotic rotational features of galaxies are easily calculated. The need for dark matter in galaxies is obviated.