Modeled homogeneous disk, star, and total intensities, photocenter and FWHM spectra (from top to bottom) when the center of the disk and the star are separated by 0.2 pixel and the slit is oriented towards the major and minor axes of the disk (left and right panels). The effect of shifting the disk center along the disk major axis, minor axis, and 45° from both are indicated with the dashed, dotted, and solid lines in the photocenter and FWHM panels. A disk radius of 0.45 pixels, brightness contrast c_cont = 10 magnitudes, and a seeing of 5 pixels is assumed in all cases.