We attempt to measure possible miscalibration of the wavelength scale of the VLT-UVES spectrograph .
We take spectra of QSO HE0515-4414 through the UVES iodine cell which contains thousands of well-calibrated iodine lines and compare these lines to the wavelength scale from the standard thorium-argon pipeline calibration .
Analyzing three exposures of this z = 1.71 QSO , we find two distinct types of calibration shifts needed to correct the Th/Ar wavelength scale .
First , there is an overall average velocity shift of between 100 m s ^ { -1 } and 500 m s ^ { -1 } depending upon the exposure .
Second , within a given exposure , we find intra-order velocity distortions of 100 m s ^ { -1 } up to more than 200 m s ^ { -1 } .
These calibration errors are similar to , but smaller than , those found earlier in the Keck HIRES spectrometer .
We discuss the possible origins of these two types of miscalibration .
We also explore the implications of these calibration errors on the systematic error in measurements of { \Delta \alpha \over \alpha } , the change in the fine-structure constant derived from measurement of the relative redshifts of absorption lines in QSO absorption systems .
The overall average , exposure-dependent shifts should be less relevant for fine-structure work , but the intra-order shifts have the potential to affect these results .
Using either our measured calibration offsets or a Gaussian model with sigma of around 90 m s ^ { -1 } , Monte Carlo mock experiments find errors in { \Delta \alpha \over \alpha } of between 1 \times 10 ^ { -6 } N _ { sys } ^ { -1 / 2 } and 3 \times 10 ^ { -6 } N _ { sys } ^ { -1 / 2 } , where N _ { sys } is the number of systems used and the range is due to dependence on how many metallic absorption lines in each system are compared .