\begin{table}%t1
      \caption{\label{tab1}Observing log: date, number of spectra, signal-to-noise ratio and seeing.}
      %\centering
\par
        \begin{tabular}[h]{cccc} 
            \hline \hline
             Date & Sp. number & {\it SNR} & Seeing (as) \\            
            \hline
           2001/01/02&160&325 $\pm$ 4&1.04 $\pm$ 0.02\\
           2001/01/03&149&248 $\pm$ 4&0.81 $\pm$ 0.01\\
           2001/01/04&181&292 $\pm$ 3&0.82 $\pm$ 0.01\\
           2001/01/06&181&295 $\pm$ 5&0.93 $\pm$ 0.01\\
           2001/01/08&125&291 $\pm$ 5&0.89 $\pm$ 0.02\\
           2001/01/09&153&328 $\pm$ 4&0.87 $\pm$ 0.01\\   
            \hline
	    \end{tabular}      
  \end{table}