\begin{table}%t1
%\centering
\par
\caption{Spectral and spatial properties of POLIS data for the two
types of polarizing beam splitters in the red channel.\label{tab_1}}
 \begin{tabular}{l c c l}
 \hline\hline
Camera & Red & Blue & Unit\\ \hline 
Dispersion  & 1.50 & 1.92 &  pm/pixel\\ 
Spatial sampling  & 0.145 & 0.290 & arcs/pixel\\
Detector full size & 488 $\times$ 652 & $652\times488$ & pixel\\\hline
\multicolumn{4}{c}{spectral division}\\\hline
Wavelength  &  630.1--630.35 & 396.4--397 & nm \\
Final image size & 160 $\times$ 652  & 326 $\times$ 122 & pixel  \\
Spectral $\times$ spatial & 0.24 $\times$ 96 & 0.6
$\times$ 36 &  nm $\times$ arcs \\\hline
\multicolumn{4}{c}{spatial division}\\ \hline
Wavelength  &  630.1--630.5 &-- & nm \\
Final image size & 288 $\times$ 326 & -- & pixel\\
Spectral $\times$ spatial & 0.4 $\times$ 48 & -- & nm $\times$ arcs\\ \hline
\end{tabular}
\end{table}