Illustrative example of the wavelength-dependent observables of one of the 17 η Car measurements (projected baselines up to 129 m; see Sect. 2). The panels show the wavelength dependence of flux, visibilities, closure phases, and phases of the Fourier transform of η Car. Baselinelengths and PAs of the baselines are indicated in the panels. The different colored lines are measurements taken at different times (separated by ~1 min, i.e., different atmospheric conditions) with different configurations of the MATISSE BCD.