\begin{table}%t5
    %\centering
\par
    \caption{\label{calibration_data}Calibration data (taken on the first night).}
    \small    \begin{tabular}{lllll}
        \hline\hline
                & \multicolumn{2}{l}{Instrumentational} & \multicolumn{2}{l}{Measured standard}\\
                & \multicolumn{2}{l}{polarization}      & \multicolumn{2}{l}{polarization}\\
 Band    & Value    & uncertainty  & Value    & uncertainty\\
                & (\%)     & (\%)  & (\%)     & (\%)\\
        \hline
        {\it U} & $-0.005$ & 0.030  & $+0.126$ & $0.103$\\
        {\it B} & $-0.064$ & 0.024  & $-3.607$ & $0.112$\\
        {\it V} & $-0.017$ & 0.028   & $-3.959$ & $0.166$\\
        {\it R} & $-0.011$ & 0.024   & $-4.064$ & $0.156$\\
        {\it I} & $-0.059$ & 0.029  & $-2.647$ & $0.226$\\
        \hline
    \end{tabular}
\end{table}