\begin{table}%t1
%\centering
\par
\caption{\label{tab:spec}Column densities (cm$^{-2}$) and ortho/para ratios towards Sagittarius~B2(M).}
\par
\begin{tabular}{ccccc}
\hline \hline \noalign{\smallskip}
$V$ (km~s$^{-1}$) & $O/P$ & $N$(H$_2$O) & $N$(H$_2$) & $X$(H$_2$O)\\
\hline\noalign{\smallskip}
$-$135 to $-$110& $2.35 \pm 0.3$ & $2.0 \times 10^{14}$ & $5 \times 
10^{20}$ & $4 \times 10^{-7}$ \\
$-$73   to $-$52  & $2.35 \pm 0.4$ & $3.7 \times 10^{14}$ & $6
\times 10^{20}$ & $6 \times 10^{-7}$\\ 
$-$12   to $-$7    & $2.8 \pm 0.5$   & $1.2 \times 10^{14}$ & $4
\times 10^{20}$ & $3\times 10^{-7}$\\
5           to 20        & $3.0 \pm 0.6$   & $6.7 \times 10^{15}$ &
$3 \times 10^{21}$ & $2 \times 10^{-6}$ \\
27         to 35        & $2.3 \pm 0.3$   & $1.7 \times 10^{14}$ &
$6 \times 10^{20}$ & $3 \times 10^{-7}$ \\
\hline
\end{tabular}
\vspace*{-2mm}
\end{table}