Almost all commercial heliostats are calibrated using the sun and a target placed below the central receiver. This setup limits the orientations that the heliostat can assume during calibration since the sun follows a restricted path. The calibration points, therefore, do not cover a wide range of heliostat orientations. This could lead to suboptimal calibration. This paper investigates the improvement in calibration that is possible when a heliostat's orientation covers a wider range. In practice, this is possible by placing artificial light sources throughout the heliostat field. The investigation is done using only numerical simulations. Simulations make it possible to pinpoint the sources of poor pointing accuracy, which is difficult to achieve for physical heliostats. The results show that there is around a 10% improvement in pointing accuracy when using the alternative calibration method.