\begin{table}%T6
\par
\caption{Correction of $m_{21}$ to the scale of Nan\c{c}ay. This table gives 
the the zero-point shift and the mean error
for the different radiotelescope (Col.~1). By its adoption as a standard, the Nan\c{c}ay
radiotelescope ($t=1$) has $b=0$ and its standard deviation is
$\sigma=0.24$. \label{tab6}
}
%\centering
\par
\begin{tabular}{rrrrr}
\hline\hline
 $t$ &$ b \pm \sigma_b$ & $\sigma$ &$n$& $N_{\rm s}$\\
\hline
      7&$  0.052\pm  0.016$&  0.393&   647&  4182\\
      9&$ -0.086\pm  0.013$&  0.415&  1043&  6413\\
      3&$  0.051\pm  0.012$&  0.260&   467& 12~813\\
     10&$  0.076\pm  0.015$&  0.324&   448& 13~115\\
      5&$  0.045\pm  0.013$&  0.261&   443& 13~947\\
      8&$  0.073\pm  0.013$&  0.317&   594& 13~989\\
      2&$ -0.026\pm  0.016$&  0.272&   322& 14~417\\
     14&$ -0.036\pm  0.037$&  0.305&    68& 14~426\\
     15&$  0.095\pm  0.036$&  0.405&   136& 14~443\\
     11&$  0.038\pm  0.112$&  0.515&    23& 14~497\\
     13&$  0.088\pm  0.083$&  0.371&    32& 14~498\\
     12&$ -0.036\pm  0.075$&  0.285&    22& 14~499\\
      4&$ -0.069\pm  0.088$&  0.403&    20& 14~500\\
      6&$  0.287\pm  0.174$&  0.655&    13& 14~500\\
\hline
\end{tabular}
\end{table}