Cluster members selection. Panel a: proper motion distance (μ_R) relative to NGC 1851 mean motion derived in Vasiliev & Baumgardt (2021), as a function of Gaia G magnitude. Cluster members are displayed as black shaded points, while residual field stars contaminants are shown with orange crosses. Panel b: parallax (ω) as a function of G magnitude. Panel c: uncertainty in proper motions (ϵ_μ) vs. Gaia G magnitude. Panel d: Δ RA vs. Δ Dec of the selected cluster members. Panel e: G vs. G_BP − G_RP CMD of the selected cluster members.