\begin{table}%t1
%\centering
\par
\caption{Optical observations.\label{tabla_rosario}}
\begin{tabular}{cccc}
\hline \hline
	       & Central	 &	 &	    \\ 
	      & wavelength	& {\it FWHM}  & $t$$_{\rm exp}$\\ 
  Filter       &    (\AA)	 & (\AA) & (s)      \\ \hline
 H$\alpha$ (l) & 6571		 &  47   & 2700     \\
 H$\alpha$ (c) & 6687		 &  50   & 2700     \\
 $[$SII$]$ (l) & 6724		 &  50   & 1800     \\
 $[$SII$]$ (c) & 6803		 &  50   & 2700     \\
 $[$NII$]$ (l) & 6589		 &   9   & 2700     \\ \hline
\end{tabular}
\end{table}