The present invention relates to apparatus and methods to provide a control system for the purpose of redirecting light from a source onto a target. The present invention appreciates that the optical properties of light that is both modified and/or distributed, e.g. by diffraction, diffusion, or some other process, and also redirected by a heliostat, can be a function of how the light redirecting element is aimed. This means that the aim of the light redirecting element can be precisely determined once the aim of the modified and/or distributed light is known. Advantageously, the characteristics of modified and/or distributed light indicative of how that light is aimed can be determined from locations outside the zone of concentrated illumination in which sensors are at undue risk. This, in turn, means that modified and/or distributed light characteristics can be detected at a safe location, and this information can then be used to help precisely aim the light redirecting element onto the desired target, such as a receiver in a CSP system. The aim of the modified and/or distributed light is thus an accurate proxy for the light beam to be aimed at the receiver.