\begin{table}%T1
\caption{\label{tab-calib}\Tf~and \lg\ of \hd\ derived from published Str\"omgren colours.}
\small%\centering
\par
\begin{tabular}{lcccc}
\hline\hline
  & Moon & Ribas et al. & Balona & Napiwotzki et al. \\
\hline
{\Tf}              & 7811   & 7843          & 7745    & 7664 \\
{\lg}              & 3.94    & 3.94           & 3.95     & 3.80 \\
spectral type & A7      & A7             & A7       & A8 \\
\hline
\end{tabular}
\end{table}