Real part of the visibilities as a function of the deprojected baseline. Left panel: 1.3 mm data. Right panel: 2.7 mm data. Red shaded regions are the uncertainties due the flux calibration. We show a variety of models with a maximum grain size in the envelope of a_max = 0.1, 50, 100, 300, 1000 μm. At the bottom of each panel are the residuals between the data and the best model.