Pseudo-colour image of the galaxy NGC 4523 obtained combining the NGVS (Ferrarese et al. 2012) and VESTIGE (Boselli et al. 2018a) optical u and g in the blue channel, the r and the narrow-band Hα in the green, and the i and the continuum-subtracted Hα in the red. Red contours are shown at column densities of N(HI) = 2ⁿ × 3.9 × 10¹⁹ cm⁻² with n = 0, 1, …5. The cyan contours show the i-band isophote at 24.5 mag arcsec⁻². The yellow arrow indicates the position of the cluster centre (M87), located at 0.83 Mpc projected distance.