Calibrated MIDI visibility amplitudes for different pulsation phases within the same cycle to investigate intracycle visibility variations. Each line represents a different pulsation phase within the same cycle and is computed as an average of data obtained at the respective phase ( ± 0.15) and observed at similar projected baseline length (B_p  ±  10%) and position angle (PA  ±  10%). The top panel shows the example of pulsation phases 0.45, 0.61, and 0.74 of cycle two observed with a projected baseline length of  ~29 m and a position angle of  ~70 deg. The bottom panel shows the example of pulsation phases 0.62, 0.75, and 0.83 of cycle two observed with a projected baseline length of  ~16 m and a position angle of  ~72 deg. The error bars are computed as the standard deviation of the averaged visibilities.