Adjustment of the two masks. The vertical blue line gives the wavelength position of the center of one stellar line of the observed spectrum, after telluric correction and stacking of all exposures. Its height is the contrast of the line (relative depth, 0.64). The red line represent the same line, back-shifted to account for the radial velocity Vrad₀ of the star. The velocity Vrad₀ was determined with the original mask BM1 and data from orders 92–115. As a result, the position of the red line coincides well (but not perfectly) with the corresponding line of the original BM1 mask (vertical bar, bottom).