Raw observed phase curve of WASP-18b before removal of systematics and stellar variation. The transit is shown in the inset. The observations cover two eclipses to establish a baseline; there is one transit in the middle of the observations. There is an additional half-orbit gap in the observations at 20 h due to a gyro bias update. Clear orbit-long systematics can be seen, as well as a visit-long slope, on top of the phase-curve variation. The two colours signify the exposures taken from each of the two spatial scan directions, where there is an offset due to the fixed read-out pattern of the detector.