The rotating modulation collimator is so promising as an efficient astronomical x-ray camera that the data-reduction techniques merit further development. The mathematical problem is equivalent to that encountered in connection with image formation by a thin annular-aperture pupil. An unorthodox procedure based on least-squares fitting is proposed for the requisite image synthesis. The method basically seeks the best sinusoidal fit to the measured signal phases around the pupil to locate the brightest star, subtracts its contribution to that signal, and iterates.