\begin{table}%t1
\caption{\label{table:log}Log of the observations.} 
\par
      % is used to refer this table in the text
%\centering
                          % used for centering table
\begin{tabular}{c c c c}        % centered columns (4 columns)
\hline\hline \noalign{\smallskip}
                % inserts double horizontal lines
Date & $n\times \exp$. time (s) & Filter & Telescope \\    % table heading 
\hline                        % inserts single horizontal line
2001 June 28 & $1\times 600$ & $r'$     & 6.5~m Magellan  \\
             & $1\times 600$ & $i'$    &  \\
             & $1\times 600$ & $z'$    &  \\
2001 July 09  & $5\times 60$ & $H$     & 3.8~m UKIRT\\
             & $5\times  60$ & $K$     &  \\
2007 April 25  & $3\times  900$ & $V$     & 1.5~m San Pedro M\'artir \\
             & $3\times  600$ & $R$     &  \\
             & $3\times  600$ & $I$     &  \\ 
2007 April 26  & $3\times  300$ & $R$     &  6.5~m Magellan \\
2007 April 27  & $3\times 300$ & $I$     &  6.5~m Magellan \\
2007 July 16  & $1\times  1800$ & $R$     & 3.6~m La Silla \\
             & $1\times  1800$ & $i$     &  \\
\hline                                   %inserts single line
\end{tabular}
\end{table}