RGB image of PLCK G128.38+71.18 obtained with the WFC/INT. The small white circle shows the Planck position. The yellow circle indicates our proposed counterpart, WHL J124204.5+454439, at a redshift of z = 0.3367. The green circle shows another cluster that we have spectroscopically confirmed, at z = 0.5775. The light blue contours correspond to the 2.5 × 10^-6 and 4 × 10^-6 levels of the Compton y-map in this area (Planck Collaboration XXI 2014). See text for details.