Phase function of asteroid (673) Edda. The top panel shows the original measurements in cyan and orange filters; the brightness (relative flux) was normalized to a unit distance from the Sun and Earth, and outliers were removed. The vertical shift between two filters corresponds to the color index c− o = 0.402 mag. On the bottom panel, the rotation and geometry effects were removed and the solid curves correspond to phase-angle functions according to Eq. (2) with different slope parameters k_c and k_o. The scatter of points around the mean phase curves corresponds to residuals of the fit.