This paper addresses alternative procedures to the ESO supplied pipeline
procedures for the reduction of UVES spectra of two quasar spectra to determine
the value of the fundamental constant mu = Mp/Me at early times in the
universe. The procedures utilize intermediate product images and spectra
produced by the pipeline with alternative wavelength calibration and spectrum
addition methods. Spectroscopic studies that require extreme wavelength
precision need customized wavelength calibration procedures beyond that usually
supplied by the standard data reduction pipelines. An example of such studies
is the measurement of the values of the fundamental constants at early times in
the universe. This article describes a wavelength calibration procedure for the
UV-Visual Echelle Spectrometer on the Very Large Telescope, however, it can be
extended to other spectrometers as well. The procedure described here provides
relative wavelength precision of better than 3E-7 for the long-slit
Thorium-Argon calibration lamp exposures. The gain in precision over the
pipeline wavelength calibration is almost entirely due to a more exclusive
selection of Th/Ar calibration lines.Comment: Accepted for publication in New Astronom