WASP-79b white light curves for visit #65 (left) and #66 (right). Top: normalised raw light curves. Middle: flux corrected from systematic errors and fitted with a transit model. Bottom: residuals between the flux corrected spectra, the best-fit models, and 2-σ error bars (dotted line). Visit #65’s raw data display a large ramp effect compared to visit #66. This ramp is mainly correlated to the HST orbital phase.