\begin{table}%t1
\caption{\label{tab:mag}Observational data.}
%\centerline
{\small
\begin{tabular}{c c c c} \hline \hline
Instrument    & Band  & Integration            & Limiting \\ 
              &         &  time (h) & magnitude\tablefootmark{a}\\ \hline 
MegaCam   &         $u^\ast$     &     20.7           &  27.9\\ 
MegaCam   &         $g'$     &       25        &  28.1\\
MegaCam   &         $r'$     &       49         &  27.8\\
MegaCam   &         $i'$     &       74         &  27.4\\
MegaCam   &         $z'$     &       55.8         &  26.5\\ \hline
WIRCam    & NB 1st epoch  &           20           &  24.8\\
WIRCam    & NB 2nd epoch  &           20           &  24.9\\
WIRCam    & NB combined   &           40           &  25.2\\
WIRCam    &     $J$     &     6.2     &  25.0\tablefootmark{b} \\ 
WIRCam    &     H     &       7.7      &  24.7\\ 
WIRCam    &     $K_{\rm s}$    &    8.9  &  24.7\tablefootmark{b} \\ \hline
IRAC      &  3.6 $\mu$m   &      0.034           &  22.2 \\
IRAC      &  4.5 $\mu$m   &     0.034           &  21.5 \\ \hline
\end{tabular}}
\vspace*{-1.5mm}
\tablefoot{\tablefoottext{a}{$4 \sigma$ magnitude limits in apertures 1.5\arcsec\
in diameter for MegaCam and WIRCam. These limits correspond to a 50\% 
completeness level. IRAC limiting magnitudes are 5$\sigma$ in 3.8\arcsec\ 
apertures.}
\tablefoottext{b}{In one quarter of the field, for which additional 
NTT/SOFI data were available, magnitude limits of 25.2 in $J$ and 24.8 in $K_{\rm s}$ 
were achieved.}}
\end{table}