\begin{table}%t1
\caption{\label{tab:cal}Calibrators list.}
%%\centering

\small
\begin{tabular}{cccl}
\hline\hline
Epoch & Frequency & Observing time & Phase calibrators\\
yy-mm-dd & GHz & hour&\\
\hline
03-08-07&1.6&1.0&J1350+3034\\
08-02-26&1.6&1.0&J1342+2709 \\
97-04-06&5.0&1.0&J1350+3034\\
05-07-27&5.0&1.5&J1342+2709\\
08-02-26&5.0&1.5&J1342+2709\\
08-02-26&8.4&2.0&J1342+2709\\
08-02-26&22&3.5&J1342+2709\\
\hline
\end{tabular}
\end{table}