TRGB edge detection for NGC 1052–DF2. Top row: the CMD (left panel), the binned and smoothed F814W luminosity function (middle panel), and its response function to a sobel kernel (right panel) are shown for stars located at R_eff < R < 4R_eff. Black points are stars that pass quality cuts, and the luminosity function is calculated for stars that pass an additional color cut to select the RGB (the diagonal dashes lines). Crosses indicate photometric scatter. The dashed orange line indicates the steep increase in the F814W luminosity function that we identify as the TRGB, measured by fitting a Gaussian, m_TRGB,F814W = 27.52 ± 0.17 mag, while the dotted orange line marks the TRGB for 13 Mpc (Trujillo et al. 2019). Bottom row: the CMDs of stars in radial bins. The dashed line indicates the respective TRGB measurement.