\begin{table}%t1 \caption{\label{photour}Photometric solutions available in this work.} \small%\centerline { \begin{tabular}{cccc} \hline \hline Passband & $ZP$ & $k$ & $CT$ \\ \hline $B$ & $24.66 \pm 0.005$ & 0.22 & $0.26 \pm 0.007$ \\ $V$ & $24.23 \pm 0.006$ & 0.11 & $-0.15 \pm 0.012$ \\ $R$ & $24.50 \pm 0.007$ & 0.07 & $-0.02 \pm 0.015$ \\ \hline \end{tabular}} \medskip Column~1 the passband; Cols.~2$-$4 the zeropoint in the Vega magnitude system ($ZP$), the extinction coefficient~($k$), and the colour term~($CT$) together with their errors. These ``best fit'' parameters were obtained from a two-parameter fit to about 200~measurements across the WFI~field for each passband, the extinction coefficient being fixed. \end{table}