Top panel: variation in the planetary radius, in terms of the planet-to-star radius ratio, with wavelength. The points are from the ground-based transit observations presented in this work (black from the MPG 2.2 m telescope and grey from the Danish 1.54m telescope). The vertical bars represent the errors in the measurements and the horizontal bars show the FWHM transmission of the passbands used. The observational points are compared with three synthetic spectra from Fortney et al. (2010, Red: equilibrium-chemistry; Blue: no TiO, VO opacity; Green: enhanced Rayleigh scattering). The same offset is applied to all four models to provide the best fit to the measurements. The size of 10 atmospheric pressure scale heights (10 × H) is shown on the right of the plot. Bottom panel: transmission curves for the Bessell I and R filters and the total efficiencies of the GROND filters.