\begin{table}%t2
\caption{Main-beam efficiencies ($\eta_{{\rm mb}}$), and main-beam FWHM: s ($\theta_{{\rm mb}}$), at the frequencies of the CO lines.}\label{efficiencies}
$$
\begin{array}{ccccccccc}
\hline\hline
\multicolumn{1}{c}{{{\rm Transition}}} &&\multicolumn{1}{c}{{{\rm Frequency}}} &&
\multicolumn{1}{c}{\eta_{{\rm mb}}}  && \multicolumn{1}{c}{\theta_{{\rm mb}}} &
\multicolumn{1}{c}{{{\rm Telescope}}} \\ 
&&\multicolumn{1}{c}{{{\rm [GHz]}}} && && \multicolumn{1}{c}{{{\rm ['']}}} & \\
\hline
J=1\rightarrow0 && 115.271     && 0.43 && 33 & {\rm OSO} \\
J=2\rightarrow1 && 230.538    && 0.66 && 21 & {\rm JCMT} \\
J=3\rightarrow2 && 345.796    && 0.62 && 14 & {\rm JCMT} \\	
J=4\rightarrow3 && 461.041    && 0.5\phantom{0} && 11 & {\rm JCMT} \\	
J=6\rightarrow5 && 691.473    && 0.3\phantom{0}  && 8 & {\rm JCMT}\\	
\hline
\end{array}
$$
\end{table}