Normalised response matrices (X) versus zenith angle (z) obtained for the E-ELT’s two Nasmyth configurations considered and for the approximated limits of the wavelength range studied (λ =  [550,850]    nm). Solid and dashed lines correspond to the lateral and straight-through configurations, respectively. Plus and cross markers denote wavelengths of λ =  [550,850]    nm, respectively. The light-green areas represent the range of values inside the requirements adopted in this study (see Sect. 3).