\begin{table}%t1
\caption[] {\label{tab:comparisons_dm}
%r.m.s. errors of the magnitude differences (instrumental system) between 
rms errors of the magnitude differences (instrumental system) between 
the comparison stars in units of 0.1~mmag.
$N$ is the total number of magnitude differences.
}
\begin{tabular}{lrrrrr} \hline
\hline
Objects                    &  $N$ & $y$ & $b$ & $v$ & $u$ \\ 
\hline
DW\,Car                     &     &     &     &     \\
HD~93191,  HD~92072  (C1,C2) & 141 &  50 &  47 &  44 &  62  \\
HD~93191,  HD~92288  (C1,C3) & 279 &  59 &  56 &  56 &  79 \\
HD~92072,  HD~92288  (C2,C3) & 115 &  69 &  58 &  63 &  88 \\
\hline
BF\,Cen                     &     &     &     &     &     \\
HD~100942, HD~101466 (C1,C2) & 989 &  40 &  37 &  35 &  53  \\
\hline
AC\,Vel                     &     &     &     &     &     \\
HD~93943,  HD~92757  (C1,C2) &1678 &  37 &  35 &  58 &  66 \\
\hline
NSV5783                    &     &     &     &     &     \\
HD~108925, HD~109808 (C1,C2) & 413 &  49 &  41 &  43 &  59 \\
\hline
\end{tabular}
\end{table}