\begin{table}%t1
\caption{Date of observations, and number of frames (nof) obtained at
each optical band.}\label{tab1}
%\centering
\par
\begin{tabular}{lcccc} 
\hline \hline
Date & $B$ & $V$ & $R$ & $I$ \\
     & (nof) & (nof) & (nof) & (nof) \\
\hline
26/03/01 & -- & -- & 24 & 24 \\
18/04/01 & 16 & 16 & 17 & 16 \\
19/04/01 & 5  & 5  & 5  & 5  \\
23/05/02 & 27 & -- & -- & 27 \\
28/05/02 & 19 & -- & -- & 19 \\
29/05/02 & 24 & -- & -- & 24 \\
20/05/02 & 24 & -- & -- & 24 \\
\hline
\end{tabular}
\end{table}