\begin{table}%t3
%\centering
\par
\caption{\label{tab:IBIS_param}IBIS instrumental parameters.}
\begin{tabular}{lc}
\hline\hline\noalign{\smallskip}
 Entrance pupil diameter    & 762 mm     \\
Effective focal length   & 18810.5 mm \\		                    
Working wavelength       & 6302~\AA   \\
FPI~\#1 plate separation & 2.300 mm   \\
FPI~\#2 plate separation & 0.637 mm   \\
Coating reflectivity     & 0.93   \\
       \hline
     \end{tabular}
		\end{table}