\begin{table}%t3
%\centering
\par
\caption{Central wavelengths and dispersions of the Gauss filter
simulating the transmissivity functions.}
%Ed:. The values for the $uvby$
%(Str\"omgren) photometric system are taken from \citet{cox}. Values
%for the $\Delta a$ system (colours $g_1$ and $g_2$) are taken
%from \citet{kupzen}.} 
\label{uvby}
\small
\begin{tabular}{lcccccc}
\hline\hline
Colour              & ${u}$& ${v}$& ${b}$& $g_1$ & $g_2$ & ${y}$\\
\hline\noalign{\smallskip}
${\lambda_a}$ [\AA] & 3500 & 4100 & 4700 & 5000 & 5220 & 5500\\
${\sigma_a}$  [\AA] & 230  & 120  & 120  &  65  &  65  & 120 \\
\hline
\end{tabular}
\end{table}