Folded NTT-EFOSC2 Hβ-continuum photometry of the central star of Hen 2-155 with the nightfall model overlaid in red (upper panel). Binned residuals between the observed photometry and model are shown in the middle panel. Note that the size of the points represents the photometric uncertainty and contain no estimate of the uncertainty due to variable nebular contamination (which can be significant, at certain phases). The lower panel shows the radial velocity measurements of the central star of Hen 2-155 with the predicted radial velocity curve from the nightfall model overlaid in red.