\begin{table}%t3                    
  \caption{\label{tab:calibrators}The flux densities and spectral indices of the standard calibrators.}
\par
     %\centerline
{  \small                  
  \begin{tabular}{l c c c c c c } 
    \hline\hline                 
    Source &$S_{4.85}$ &$\left\langle S_{4.85}\right\rangle ^\dagger$ &$S_{10.45}$ &$\left\langle S_{10.45}\right\rangle ^\dagger$ &$\alpha_{1.4}^{4.85}$   &$\alpha_{4.85}^{10.45}$ \\    
           &(Jy)  &(Jy)      &(Jy) &(Jy)      &                      &   \\    
    \hline                         
    3C~48     & 5.63 & 5.52  & 2.68  & 2.59   &$-$0.88   &$-$0.98 \\   
    3C~161    & 6.61 & 6.71  & 2.99  & 3.03   &$-$0.82   &$-$1.03 \\   
    3C~286    & 7.50 & 7.48  & 4.44  & 4.48   &$-$0.54   &$-$0.67 \\   
    NGC~7027  & 5.40 & 5.46  & 5.83  & 5.96   &$+$1.12   &$+$0.11 \\   
    \hline                                  
  \end{tabular}}
\par
  \medskip
   Columns~2 and 4 give the flux densities assumed for these
    sources. The flux densities and the spectral indices in Cols.~3,~5 and~6, 7 respectively, are the ones averaged over our   measurements.
  $^\dagger$ The average has been done over 
  data with $\textit{SNR} \ge 5\sigma$.
\end{table}