Waterfall plots of MYSTIC science-channel OPD residuals during dual-field observations of α Psc B (MJD = 60918). The waterfall plot shows the amplitude and position of the Fourier transform of a scan through the interferogram over time. Stable fringe packets are visible on all 15 baselines despite fringe-tracking residuals, demonstrating successful phase referencing from component A and enabling direct detection of the Ba–Bb subsystem. Each subpanel corresponds to one of the 15 baselines, labeled by the beam pair (e.g., 12 = Telescope 1–2) for the beam order E1–W2–W1–S2–S1–E2. Time increases horizontally, and OPD is plotted vertically; brighter lines in each waterfall window indicate higher fringe contrast and successful fringe detection. The brighter double lines in some of the large baseline waterfall windows are an indication of Ba–Bb binary is resolved. The coherent fringe integration time for this diagnostic is 10 ms.