\begin{table}%t1
%\centering
\par
\caption{N$_2$H$^+$(1--0) observing parameters.\label{table:param}}
\begin{tabular}{lccll}\hline\hline
Telescope     &
$\Delta \Theta$  &
$\eta_{\rm mb} $ &
$T_{\rm sys}$       &
$\delta V$         \\
         & ($\arcsec$) &           & (K)       & (km s$^{-1}$)\\
\noalign{\smallskip}\hline\noalign{\smallskip}
OSO-20~m  & 40     & $\sim$0.5   & 250--500  & 0.8; 0.16\\
SEST-15~m & 55     & 0.75         & 200--300  & 0.14\\
\hline
\end{tabular}
\end{table}