The overlap agreement between the red edge of the 25th NRES diffraction order and the blue edge of the redder 24th diffraction order. Both spectra have been blaze-corrected (see Appendix A). The two orders are shifted in the top panel so that they are aligned at a duplicated feature at x = 3050, highlighted by the dashed black line. In each panel, the horizontal scale of order 24 has been transformed by a map g(x) whose form is indicated in the upper left. The coefficients ﹩a,b,...﹩ of g(x) in each panel (except the uppermost) maximize the number of matched features.