Comparison of the observed (black dots) and synthetic (solid red line) spectra for the M3.0 V star J00570+450 (G 172–30) in the spectral region around λλ15 750 Å. Some OH lines, from which the O abundance was derived, and less intense Mg I lines near λλλ15740, 15749, and 15765 Å are markedand labelled. In this region the pseudo-continuum is reduced mainly due to the contribution of an H₂O veil.