Telluric line corrected spectrum of the flux standard white dwarf EG 274 (black), pipeline flux-calibrated spectrum (red) for comparison, catalogued flux (blue), and limits to identify detector artefacts (thin purple) in the upper panel, the telluric transmission model in the middle panel, and the residuals (telluric corrected minus catalogued flux) in the bottom panel of the plots. Residuals are typically a small percentage of the actual flux value. Typical statistical uncertainties of the residuals are smaller than the plot symbols. We do not include the uncertainty of the absolute flux calibration here. Extreme residuals due to detector artefacts fall outside the displayed range. See text for further comments on the construction of this figure.