\begin{table}%t1
\caption{\ch-LETGS observation log of \mrk.}\label{t:obs_log}
%\centering
\small
\begin{tabular}{lll}
\hline
\hline
ObsId & Exp  & date\\
	& (ks) & dd-mm-yy\\
\hline
4401 &	55	&	$10-05-03$	\\
4027 &	100 	& 	$12-05-03$	\\
4400 &  50  	&	$14-05-03$	\\
4428 &	50	&	$15-05-03$	\\
4429 &	50	&	$17-05-03$	\\
4427 &	27.5	&	$19-05-03$	\\
4436 &	27.5	&	$20-05-03$	\\
\hline
\end{tabular}
\end{table}