Test #1 of the influence of phase gaps and filled gaps. Each image is shown in four spherical projections 90° apart. a) Input map. This map is identical to the first reconstruction from season 2007/08 (DI #8 from 2007.67) with a total of 21 phases. b) The reconstruction when ignoring phases No. 4–9 in the inversion process. c) The (absolute) difference a − b. d) The reconstruction when the phase gap is filled with phases from the following stellar rotation. e) The (absolute) difference a − d.