\begin{table} %t1
%\centering
\par
\caption{Observation log of NGC~6253.}\label{obs6253}
\begin{tabular}{llllll}
\hline
\hline
Date   & UT$_{\rm{beginning}}$ &Exposure time&Configuration &Grating& No. of stars\\
& &(s) & && \\
\hline
2004-04-07&07 31 40.549&2595 &A &CD3 & 7\\
2004-04-08&07 39 50.833&2595 &B &CD3 & 6\\
2004-04-06&08 34 34.455&2595 &A &CD4 & 7\\
2004-04-07& 08 27 40.831&2595&A &CD4 & 7\\
2004-04-08&08 37 19.858&2595 &B &CD4 & 6\\
\hline
\end{tabular}
\end{table}