The usual procedure is to identify an easily recognizable line in the stellar spectrum such as hydrogen or sodium to determine the radial velocity correction. The unknown lines are then measured and corrected for the star's radial velocity. The corrected line values are then checked against the wavelength tables. The presence of an element in the spectra is generally confirmed by identifying several lines of that element in the spectra. The most common elements with easily measured lines are hydrogen, helium, sodium, iron, nitrogen, carbon and oxygen.
Many spectra have dozens of iron lines that can be identified.
The measured radial velocity correction of the star can be compared with the value in Wilson's book to determine the contribution from the Earth's motion in space. Analysis of line width is a complex subject. The observed line width is the convolution of the instrument narrow line response with the actual star line. The instrument's narrow line response may be approximated by measuring the profile of the calibration source lines. Its half width will be approximately equal to the resolution of the setup, 2.5 Angstroms for the high resolution mode and ten angstroms for the low resolution mode.