\begin{table}%t4
\caption{Central wavelengths and dispersions of the Gauss filter simulating the
transmissivity functions of $uvby$ (Str\"omgren) photometric system.
These values are taken from \citet{cox}.}
\label{uvby}
%\centering
\small
\begin{tabular}{lcccc}
\hline
\hline
Colour              & ${u}$& ${v}$& ${b}$& ${y}$\\
\hline
${\lambda_a}$ [\AA] & 3500 & 4100 & 4700 & 5500\\
${\sigma_a}$  [\AA] & 230  & 120  & 120  & 120 \\
\hline
\end{tabular}
\end{table}