\begin{table}%T2
%\centering
\par
  \caption{
   \label{tab-cmprms}
    rms scatter of the PMT magnitude differences (mmag) 
    between comparison stars. $N$ is the number of differential
    measurements.
   }
   \begin{tabular}{l r l l l l}
      \hline
      \hline
      \noalign{\smallskip}
      Compared pair &              $N$ & $y$ & $b$ & $v$ & $u$ \\
      \hline
      \object{NGC~3293-20}, \object{HD~92072} (C1,C2)& 668 & 6 & 6 & 6 & 7 \\
      \object{NGC~3293-20}, \object{HD~91477} (C1,C3)& 368 & 6 & 6 & 6 & 7 \\
      \object{HD~92072}, \object{HD~91477} (C2,C3)&   1068 & 6 & 6 & 7 & 9 \\
      \hline
       \end{tabular}
\end{table}