\begin{table}%t5
\caption{\label{tbl:ground_based}Datasets described in this paper and frequency values for the dominant mode determined from a Scargle periodogram \citep{scargle1982}$^\dagger$.}
\small%\centerline
 {
\begin{tabular}{lcrrlll}
\hline\hline
&&&&&& \\[-8pt]
 & $t_0$ (y) & $T$~(d) & $n$ & $f$ (d$^{-1}$) & $\sigma_f$
(d$^{-1}$) & $f$ ($\mu$Hz)\\
\hline
Hipparcos     & 1990 & 1091 & 83       & 5.4871  & 0.00006  & 63.508(2)\\
Swiss 70 cm/P7 & 1997 & 187  & 20       & 5.4869  & 0.0002  & 63.50(5)\\
Mercator/P7   & 2002 & 1184 & 171      & 5.48693 & 0.00001 & 63.506(1)\\
ASAS          & 2001 & 2798 & 310      & 5.48691 & 0.00001 & 63.505(9)\\
CoRoT/SISMO   & 2007 & 156  & 379~785 & 5.48689 & 0.00003 & 63.505(7)\\ 
\hline
All           & 1990 & 6814 & 380~369 & 5.48694 & 0.00003 & 63.506(3)\\ 
\hline
\end{tabular}}
\medskip
$\dagger$: $t_0$: starting time of observations, $T$: total timespan, $n$: number of measurements,
$f$: frequency value, $\sigma_f$: error on frequency.
\end{table}