\begin{table}%t1
%\centering
\par
\caption{The COMBO-17 filter set: exposure times and~10$\sigma$ magnitude 
limits reached for point sources, averaged over all three fields. The $R$-band 
observations were selected to be taken under the best seeing conditions ($FWHM$
$0\farcs55\ldots0\farcs8$). See also Fig.~\ref{qeff}.
\label{filterset}}
\begin{tabular}{llrc}
\hline \hline
\multicolumn{2}{l}{$\lambda_{{\rm cen}}$/$fwhm$ \rm (nm)}  & $t_{\rm {\rm exp}}$/s & 
 $m_{\rm {\rm lim},10\sigma}$ \\ 
\noalign{\smallskip} \hline \noalign{\smallskip} 
364/38 &  $U$ &  20~000 & 23.7 \\ 
456/99 &  $B$ &  14~000 & 25.5 \\ 
540/89 &  $V$ &   6000 & 24.4  \\
652/162 & $R$ &  20~000 & 25.2 \\ 
850/150 & $I$ &   7500 & 23.0 \\
\noalign{\smallskip} 
420/30  &      &  8000 & 24.0 \\ 
462/14  &      & 10~000 & 24.0 \\ 
485/31  &      &  5000 & 23.8 \\ 
518/16  &      &  6000 & 23.6 \\ 
571/25  &      &  4000 & 23.4 \\ 
604/21  &      &  5000 & 23.4 \\ 
646/27  &      &  4500 & 22.7 \\
696/20  &      &  6000 & 22.8 \\ 
753/18  &      &  8000 & 22.5 \\ 
815/20  &      & 20~000 & 22.8 \\ 
856/14  &      & 15~000 & 21.8 \\ 
914/27  &      & 15~000 & 22.0 \\
 \hline
\end{tabular}
\end{table}