Determination of average radial velocity for each cluster. Filled symbols mark those stars used to determine the average value, while open symbols are the excluded objects. Black circles represent those stars observed with MERC, NOT1, and NOT2, while green diamonds are the stars observed with CAH2. Red pentagons are the known spectroscopic binaries. Arrows denote objects outside the panels. Dot-dashed lines correspond to the average radial velocity for each cluster. Dotted lines show the 3 × σ_vrad level. We note that in most of the cases, error bars are smaller than the symbol size. All source identifications are from Gaia EDR3.