Squared visibility vs. spatial frequency for HD 131156 and HD 146233. The HD number is noted in the upper right corner of each plot. The raw error bars were scaled to the reduced χ² before the final fitting. For HD 131156 the reduced χ² = 4.7 and for HD 146233 χ² = 3.7. The grey dots are the individual PAVO measurements in each wavelength channel. For clarity, the weighted averages of the PAVO measurements are shown as red circles. The green line shows the fitted limb-darkened model to the PAVO data, with the light grey shaded region indicating the 1σ uncertainties. Lower panel: residuals from the fit.