Survey data release 10 [SDSS DR10, @Ahn2014] counterpart, and applying this scaling-solution to the target. For point-sources, this prevents temporally varying seeing and slit-losses from propagating into systematic errors which would be introduced in calibrating against spectrophotometric standard stars. However, it does not account for any flux variation caused by intrinsic quasar variability. Based on the the same FORS2 data for Q1323-0021, [@Moller2018] quantify the effect of quasar variability on the flux-calibration. In their work, they find that flux-measurements are correct to within a factor of two, with quasar variability responsible for $\sim 10\%$, and slit losses for the remaining fraction.

The SDSS catalogue does not cover HE1122-1649. In this field, we assume that the transmission is the same as for the other fields observed with the same instrument settings. This allows us to calculate an average sensitivity function which we use to flux calibrate the spectrum in the HE1122-1649 field. Based on five sensitivity functions, we calculate an RMS of $0.5 - 0.8 \times 10^{-17}~\mathrm{ergs}~\mathrm{s}^{-1}~\mathrm{cm}^{-2}$ in the wavelength region $\lambda\lambda 6000-8000~\mathrm{\AA}$. This RMS value is of the same order as integrated line-flux uncertainties (see Table \[tab:line-fluxes\]), and accounts for weather conditions, slit-losses and quasar variability effects. We therefore confirm 