\begin{table}%t1
%\centering
\par
\caption{Information about the 1996, 1998, and 2005 data in both filters.}   \label{tab:oss}
   \begin{tabular}{lccc}
   \hline
   \hline
   Obs. ID   & Date        & Exposure time & Filter       \\
            &             & (s)           &              \\
   \hline
  u31f0107t & 1996 Feb. 03 & 1300          & [SII]        \\
  u31f0108t & 1996 Feb. 03 & 1200          & [SII]        \\
  u31f0109t & 1996 Feb. 03 & 1300          & H$_{\rm \alpha}$ \\
  u31f010at & 1996 Feb. 03 & 1200          & H$_{\rm \alpha}$ \\
  % \hline
  u3nj0101r & 1998 Mar. 15 & 1300          & [SII]        \\
  u3nj0102r & 1998 Mar. 15 & 1300          & [SII]        \\
  u3nj0103r & 1998 Mar. 15 & 1300          & H$_{\rm \alpha}$ \\
  u3nj0104r & 1998 Mar. 15 & 1300          & H$_{\rm \alpha}$ \\
  % \hline
  u9570201m & 2005 Jan. 22 & 1200          & [SII]        \\
  u9570202m & 2005 Jan. 22 & 1200          & [SII]        \\
  u9570101m & 2005 Jan. 21 & 1200          & H$_{\rm \alpha}$ \\
  u9570102m & 2005 Jan. 21 & 1200          & H$_{\rm \alpha}$ \\
   \hline
   \end{tabular}
   \end{table}