\begin{table}%t2
\caption{\label{optlog}Log of optical observations.}
\small
%\centering
\par
\begin{tabular}{lllcrcc}
\hline    
\hline    
Cluster & Survey & Obs. date     & Filter & \multicolumn{1}{c}{Exp.} & $m_{\rm comp}$, $m_{\rm lim}$ & Airmass \\
        &        & (UT)          &        & \multicolumn{1}{c}{(s)}  & (mag)                         &         \\
\hline    
\so     & Palomar& 2002 Feb. 07   & $i'$   & 46~$\times$~200            & 23.2, 24.5                    & 1.38--1.39 \\ 
        & Palomar& 2002 Feb. 07   & $z'$   & 21~$\times$~200            & 22.5, 24.0                    & 1.40--1.93 \\ 
        & Calar  & 2003 Dec. 23   & $i'$   & 26~$\times$~500            & 23.8, 24.5                    & 1.30--1.93 \\ 
        & Calar  & 2003 Dec. 24   & $z'$   & 26~$\times$~600            & 22.8, 24.0                    & 1.30--1.95 \\ 
Praesepe& Palomar& 2002 Feb. 07   & $i'$   & 28~$\times$~200            & 23.8, 24.8                    & 1.03--1.23 \\ 
        & Palomar& 2002 Feb. 07   & $z'$   & 21~$\times$~200            & 23.3, 24.3                    & 1.25--1.80 \\ 
        & Calar  & 2003 Dec. 23   & $i'$   &  9~$\times$~500            & 23.3, 24.5                    & 1.05--1.13 \\ 
        & Calar  & 2003 Dec. 23$-$24& $z'$   & 18~$\times$~500            & 22.8, 24.0                    & 1.05--1.44 \\ 
\hline    
\end{tabular}
\end{table}