\begin{table}%t2
%\centering
\par
\caption{Coefficients of the transformation to the standard system for each filter
and for each chip. Column~3 gives the number of standard stars used to derive
the zero points and the color terms (Cols.~4 and~5), imposing the mean extinction 
coefficients of La Silla (Col. 6); finally, Col. 7 gives the corresponding average 
standard errors.}\label{calib3960}
\begin{tabular}{ccccccc} 
\hline
\hline
Filter& Chip $\#$& N. stars& Zero point& Color term &Extinction& 
Av. St. error\\
\hline
$V$   &1	 & 24	&$0.987 \pm 0.007$&    $-$0.097 &0.14	& 0.034\\
      &2	 &306	&$1.022 \pm 0.002$&    $-$0.097 &0.14	& 0.031\\
      &3	 &136	&$1.062 \pm 0.003$&    $-$0.097 &0.14	& 0.030\\
      &4	 &  4	&		  &    $-$0.097 &0.14	&     \\
      &5	 &  0	&		  &    $-$0.097 &0.14	&     \\
      &6	 & 51	&$1.095 \pm 0.005$&    $-$0.097 &0.14	& 0.033\\
      &7	 & 67	&$1.048 \pm 0.003$&   $-$0.097 &0.14	& 0.022\\
      &8	 & 11	&$0.982 \pm 0.007$&    $-$0.097 &0.14	& 0.024\\
\par
\hline
\par
$B$	&1	 & 25	&$0.668 \pm 0.012$&   0.249 &0.25 	& 0.053\\
 	&2	 &328	&$0.723 \pm 0.002$&   0.249 &0.25 	& 0.038\\
 	&3	 &148	&$0.772 \pm 0.002$&   0.249 &0.25 	& 0.028\\
	&4	 &  4	&		  &   0.249 &0.25 	&   \\
	&5	 &  0	&		  &   0.249 &0.25 	&   \\
 	&6	 & 49	&$0.810 \pm 0.008$&   0.249 &0.25 	& 0.054\\
	&7	 & 56	&$0.754 \pm 0.004$&   0.249 &0.25 	& 0.030\\
	&8	 & 11	&$0.697 \pm 0.019$&   0.249 &0.25 	& 0.062\\
\par
\hline
\par
$I$	&1	 & 22	&$1.989 \pm 0.012$&   0.130 &0.09      & 0.056\\
 	&2	 &248	&$2.042 \pm 0.002$&   0.130 &0.09      & 0.035\\
 	&3	 &123	&$2.063 \pm 0.003$&   0.130 &0.09      & 0.038\\
	&4	 &  6	&		  &   0.130 &0.09      &    \\
	&5	 &  0	&		  &   0.130 &0.09      &    \\
 	&6	 & 42	&$2.072 \pm 0.007$&   0.130 &0.09      & 0.047\\
	&7	 & 47	&$2.066 \pm 0.005$&   0.130 &0.09      & 0.033\\
	&8	 & 13	&$2.009 \pm 0.007$&   0.130 &0.09      & 0.026\\
\hline
\end{tabular}
 \end{table}