Empirical Monte Carlo (EMC) distributions in the Hα line for the first (left) and second (middle) nights observed with HARPS-N, and the night observed with EXPRES (right). The distributions are obtained using 20 000 iterations and measuring the absorption depth with a bandwidth of 0.75 Å. Each panel corresponds to the analysis of one night. In green we present the ‘out-out’ scenario, in blue the ‘in-in’, and in grey the ‘in-out’, which corresponds to the atmospheric absorption scenario. The blue-dashed vertical line marks the zero absorption level and the black-dashed line the center of the ‘in-out’ distribution.