\begin{table}%t2
%\centering
\par
\caption{\label{table_paraobs1}Parameters of the two observing runs in  November
1999 and June 2001.}
\begin{tabular}{llll}
\hline\hline
& CO(1--0) & CO(2--1) & HCN(1--0)\\
\hline
Sky frequency [GHz] & 114.88927 & 229.77414 & 88.337936\\
Beam size [arcsec] & 21.0 & 10.5 & 27.5\\
Forward efficiency & 0.9 &  0.84 & 0.9 \\
Beam efficieny  & 0.73 & 0.52 & 0.77\\
\hline
\end{tabular}
\end{table}