Effect of the gravitational field of a uniform disk on the apparent position and brightness of distant sources

Using the weak gravitational field and ray optics approximations, deflection angles are calculated for rays arriving to an observer from a distant source. The observer may be placed at an arbitrary point, including the disk itself. Angular displacements of the sources and variations of their brightness are determined for the entire celestial sphere. It is shown that oscillatory ray trajectories can arise near the disk surface. The results are used to evaluate the effect of the Galactic gravitational field on the apparent picture of extragalactic sources.