Correlated fluxes obtained with MIDI using the ATs in February 2006. Baseline lengths and orientations are indicated. Black and grey symbols correspond to data reduction using two different calibrators, observed immediately prior to or following the science target. The calibration errors are within 20%. The plotted data errors are instrumental errors. Full lines show the model prediction for the correlated fluxes on these baselines (see Sect. 5.2). The dotted and the dashed lines present the model result for position angles 140° and 150°, respectively, compared to our model with 145° shown with full lines.