Procedure for identifying stars that, based on the position in the CMDs from HST photometry and in the proper-motion diagram from Gaia eDR3, are probable members of NGC 1806. The probable members are represented with red circles in the CMDs plotted in the top panels and the bottom-left panel and in the proper-motion diagram shown in the bottom-right panel. Stars that are not located on the main evolutionary sequences in at least one CMD are represented with blue stars. The arrow plotted in the proper-motion diagram indicates the mean cluster motion, while the circle is used to select the stars that are not included in the sample of probable cluster members, due to their large proper motions (aqua stars). See the text for details.