Observation (panel a) and simulation (panel b), using COMTAILS, of comet C/2023 A3 on October 13, 2024. The depicted observed image was obtained with a Newtonian reflector of 36-cm aperture by José Carrillo from the amateur astronomical association Cometas_Obs. The simulated image was obtained with COMTAILS assuming an active area anisotropic particle ejection pattern (see text for details). The comet heliocentric and geocentric distances are 0.57 au and 0.47 au, respectively. North is up and east is to the left.