\begin{table}%t2
      \caption{Total UVOT exposure time in seconds in the $V$, $B$, $U$, $UVW1$,
$UVM2$, $UVW2$ filters or UV grism.}
         \label{uvot_obs_summary}
  %\centering
\small
         \begin{tabular}{lccccccc}
            \hline\hline
                        Date &  Exp. & Exp. & Exp. & Exp. & Exp. & Exp. & Exp. \\
            &  $V$ & $B$ & $U$ & $UVW1$ &$UVM2$ &$UVW2$ &Grism \\
                        \hline
24 Apr. & 947 & 675 & 948 & 1892 & 2843 & 3926 & 0 \\
11 May & 0 & 0 & 0 & 0 & 0 & 0 & 1941 \\
17 May & 400 & 306 & 400 & 791 & 1197 & 1598 \\
19 May & 0 & 0 & 0 & 0 & 0 & 0 & 4964 \\
                        \hline
         \end{tabular}
  \end{table}