\begin{table}%t3
\caption{\label{table2} Coefficients for Eq.~(\ref{calib3}).}              
%\centerline
{                                    
\begin{tabular}{c c c c c c c c c c c c c}          
\hline\hline                        
Night & $k_y$ & $z_y$ & $a_y$ & $\rho_{zk}$ \\    
\hline                                   
14 April 2007 & --0.155 $\pm$ 0.021 & 23.009 $\pm$ 0.031 & 0.016 $\pm$ 0.005 & --0.92 \\
15 April 2007 & --0.142 $\pm$ 0.016 & 22.989 $\pm$ 0.023 & 0.016 $\pm$ 0.005 & --0.96 \\
\hline
Night & $k_b$ & $z_b$ & $a_b$ & $\rho_{zk}$ \\    
\hline
14 April 2007 & --0.240 $\pm$ 0.031 & 23.337 $\pm$ 0.043 & 0.009 $\pm$ 0.005 & --0.97 \\
15 April 2007 & --0.210 $\pm$ 0.036 & 23.297 $\pm$ 0.050 & 0.009 $\pm$ 0.005 & --0.96 \\
\hline
Night  & $k_v$ & $z_v$ & $a_v$ & $\rho_{zk}$ \\    
\hline
14 April 2007 & --0.349 $\pm$ 0.023 & 23.051 $\pm$ 0.034 & 0.050 $\pm$ 0.006 & --0.98 \\
15 April 2007 & --0.353 $\pm$ 0.023 & 23.048 $\pm$ 0.032 & 0.050 $\pm$ 0.006 & --0.96 \\
\hline
Night &  $k_u$ & $z_u$ & $a_u$ & $\rho_{zk}$ \\   
\hline
14 April 2007 & --0.582 $\pm$ 0.036 & 23.131 $\pm$  0.052 & 0.065 $\pm$ 0.007 & --0.98 \\
15 April 2007 & --0.569 $\pm$ 0.013 & 23.117 $\pm$  0.021 & 0.065 $\pm$ 0.007 & --0.96 \\
\hline                                             
\end{tabular}}\medskip
\par
Columns 2 to 4 list the airmass extinction coefficients, $k_i$, zeropoints, $z_i$ and colour coefficients, $a_i$, for each filter as indicated with uncertainties $\sigma_k$, $\sigma_z$ and $\sigma_a$ respectively. Column 5 lists the correlation coefficient between the uncertainty in extinction coefficient, $\sigma_k$, and uncertainty in zeropoint, $\sigma_z$. This coefficient is denoted by $\rho_{zk}$.
\end{table}