Cross-dispersed X-shooter PSF and its best-fit models for the flux standard star BD+174708 in echelle order eight of the VIS arm (λ_c = 7100 Å). The fit to the spectrally averaged data (black circles) is considerably improved if a skewness term is added to the Moffat profile (dash-dotted red curve) as compared to its symmetric counterpart (dashed blue curve). The measured FWHM is 4.22 pix = 0.68″, whereas the DIMM seeing is indicated as 0.52″. The best-fit Gaussian is overplotted with a green dash-dotted line for comparison.