Complete photometric optical/NIR data set of the afterglow of GRB 080928 from Swift/UVOT (all but the last filter in the first column of the legend), ROTSE-IIIa (CR, i.e. unfiltered R-equivalent Vega magnitudes), GROND (all but the last filter in the second column of the legend), and VLT-FORS (V filter) observations. All magnitudes are given in the Vega system, with colours shifted by the values given in the legend for clarity. Downward pointing triangles indicate upper limits; uvw2 was the only filter in which only upper limits could be derived. The vertical lines mark the time of our polarimetric measurements.