Multiband ground-based light curve of CVSO 104 A+B around the time of VLT and HST observations. Different symbols, as reported in the legend, are used for the different data sets. The Hα color index, which measures the intensity of the line, is shown in the upper panel. Synthetic Hα colors based on X-shooter and UVES spectra are overplotted with asterisks in the same box. The contemporaneous TESS light curve is overplotted with grey dots to the R_C light curve. The arrows in the same box mark the periastron passages. The epoch of VLT and HST observations are marked in the lower box.