Part of the HST image of DDO68 in F606W filter, centred on the SF region Knot 3 with the LBV DDO68-V1 near its centre. The aperture, used for the ground-based photometry, is superimposed as a cycle with D_aper= 5″. Arrows show directions to the north and east. Top panel: Epoch of May 2010 (Program ID 11578, PI: A.Aloisi). Bottom panel: Epoch of December 2017 (Program ID 14716, PI: F.Annibali). The shown rectangular with width of 7 pixels (0.28 arcsec) is extracted and its light is summed-up along Y direction to perform 1D two-Gauss fitting of DDO68-V1 region. See details in Appendix A.