\begin{table}%t1
%\centering
\par
   \caption{Spectral coordinate type codes, (characters 1--4 of
      \CTYPE{k\Ci}).}
   \begin{tabular}{llccl}
      \hline\hline
      Code  & Name & Symbol & Associate  & Default \\
            &      &        & variable   & units   \\
      \hline
      \keyv{FREQ} & Frequency
                  & $\nu$
                  & $\nu$
                  & Hz \\
      \keyv{ENER} & Energy
                  & $E$
                  & $\nu$
                  & J  \\
      \keyv{WAVN} & Wavenumber
                  & $\kappa$
                  & $\nu$
                  & m$^{-1}$ \\
      \keyv{VRAD} & Radio velocity
                  & $V$
                  & $\nu$
                  & m~~s$^{-1}$ \\
      \keyv{WAVE} & Vacuum wavelength
                  & $\lambda$
                  & $\lambda$
                  & m \\
      \keyv{VOPT} & Optical velocity
                  & $Z$
                  & $\lambda$
                  & m~~s$^{-1}$ \\
      \keyv{ZOPT} & Redshift
                  & $z$
                  & $\lambda$
                  & -- \\
      \keyv{AWAV} & Air wavelength
                  & $\lambda\sub{a}$
                  & $\lambda\sub{a}$
                  & m \\
      \keyv{VELO} & Apparent radial velocity
                  & $\vv$
                  & $\vv$
                  & m~~s$^{-1}$ \\
      \keyv{BETA} & Beta factor ($\vv/c$)
                  & $\beta$
                  & $\vv$
                  & -- \\
      \hline
   \end{tabular}
   \label{ta:codes}
\end{table}