\begin{table}%tA.2
\caption{Wavelengths and Einstein coefficients ($A_{ij}$) for $^{16}$OH and $^{18}$OH averaged over hyperfine structure. The $^{16}$OH wavelengths are from \citet{brown} and \citet{varberg} and the Einstein coefficients were calculated from the line strengths of \citet{brown}. The $^{18}$OH wavelengths are from \citet{morino} with Einstein coefficients calculated from the line strengths of \citet{comben}.
\label{wavelengths}}
%\begin{center}
{\begin{tabular}{ccc}
\hline 
\hline
Transition         & Wavelength & $A_{ij}$    \\
                   &    ($\mu$m)& (s$^{-1}$)  \\
\hline
 \multicolumn{3}{l}{$^{16}$OH}                \\ 
$J=3/2$--3/2$^{a}$ & 53.2615   & 0.04559      \\
                   & 53.3512   & 0.04481      \\
$J=1/2$--3/2$^{a}$ & 79.1176   & 0.03575      \\
                   & 79.1812   & 0.03545      \\
\hline
 \multicolumn{3}{l}{$^{18}$OH}                \\
$J=5/2$--3/2       &119.9651   & 0.1364       \\
                   &120.1718   & 0.1357       \\
\hline        
\end{tabular}}
\parbox{5.5cm}{
$^{a}$ Cross ladder transition: $^{2}\Pi_{1/2}$--$^{2}\Pi_{3/2}$.  }
%\end{center}
\par
\end{table}