Optical light path of the CT from the Nasmyth platform to the CCL. P4 to P7 are folding prisms that route the beam from the Nasmyth platform to the telescope’s Coudé room. The mirrors R8 and R9 form a periscope that redirects the beam into the tunnel. At the entrance and the exit of the tunnel, respectively, the two lenses L10 and L11 recondition the light beam so it can enter the FE unit inside the CCL with a specified F-number (fixed for all telescopes). Two counter-rotating double prisms, ADC12, eventually correct for atmospheric dispersion across the wide spectral range of the spectrograph. This figure is from Pepe et al. (2014) and ESPRESSO Project documentation.