... Superflat Correction of Data An example of space-dependent calibration errors combined with poor centering is shown in Figure 1, where the differential V photometry for three stars in a single field is plotted as a function of the position on the detector. ... 374 Manfroid, Royer, Rauw, and Gosset -0.05 a b c a b c 0 0.05 0 -0.05 0.1 0.2 0.3 0.4 0.5 a b c 0.6 0 0.2 0.4 0.6 0.8 a b c 1 0 0.05 0 0.1 0.2 0.3 0.4 x position 0.5 0.6 0 0.2 0.4 y position 0.6 0.8 1 Figure 1. ...