\begin{table}%t1
\caption{\label{tab1}Data sets used in this work.}
%\centering
\small
\begin{tabular}{clr}
\hline
\hline 
Data set                &Filter           & $\#$ images $\times$ Exp. time (s)\\
\hline 
$3\times3$ ACS/WFC      & {F435W}           & $27\times 340$, $9\times12$        \\ 
inner mosaic&&\\
                        & {F625W}           & $27\times 340$, $9\times8$        \\ 
ACS/WFC                 & {F606W}           & $2\times1285$, $2\times1300$,      \\ 
$\sim$17$^\prime$       &                 & $2\times1331$, $2\times1375$      \\
                        & {F814W}           & $4\times1331$, $2\times1340$, $2\times1375$\\ 
WFPC2@\textit{HST}      & {F606W}           &$2\times 300$, $1\times600$        \\ 
$\sim$7$^\prime$        & {F814W}           & $2\times400$, $1\times 1000$       \\ 
FORS1@VLT               & $B$             & $20\times 1100$                   \\
                        & $R$             &$20\times 395$                     \\ 
WFI@2.2m              & $B$             & $1\times10$, $1\times15$, $11\times30$, $1\times40$,\\
                        &                 & $1\times60$, $1\times120$,$2\times240$, $2\times300$\\
                        & $R_{\rm C}$           & $1\times5$, $1\times10$, $1\times15$, $1\times30$, $5\times60$\\
                        & $V$             & $6\times5$, $9\times10$, $1\times15$, $3\times20$,\\
                        &                 & $2\times30$, $10\times40$, $4\times45$, $3\times60$,\\
                        &                 & $10\times90$, $7\times120$, $1\times150$, $3\times240$\\
\hline
\end{tabular}
\end{table}