Normalised radial profiles of 358P and field stars in the FORS2 data, measured for two different values of the seeing FWHM, D. The green lines indicate the aperture radius in which the light curve (Fig. 1) was measured and the corresponding flux level of 92%. The x-axis is in units of the FWHM at observation, i.e. a unit interval corresponds to 3.4 pixels for the blue dots and 5.4 pixels for the red dots.