Astrometric properties of the here studied cluster stars for M 8 (up), G333.6−0.2 (centre) and NGC 6357 (bottom). The blue, red and orange correspond to stars in our catalogues. The blue, red and orange dots correspond to the stars in our catalogue for which a reliable cross-match was found. The blue dots are confirmed cluster members, and the red and orange dots are candidate non-cluster members for which we verified the quality of the astrometric fit. The sources in orange have a reliable Gaia DR2 astrometric solution and therefore we confirm that they are not cluster members; for the sources in red we do not confirm nor reject cluster membership. The grey contours represent the density of Gaia DR2 sources brighter than G = 19 within a radius of 0.5° from the central coordinates listed in Table 1 and the black dots show all the MYStIX sources with Gaia counterparts within 1″. The first column shows the equatorial Gaia sky positions. Columns two to four show the parallax ϖ vs the proper motion (μ_α^*, μ_δ).