\begin{table}%t2
\caption{The dominant mode f1: comparison of temperature and surface gravity 
mean values and semi-amplitudes from different data sets.}
\label{Tab_f1_all}
%\centering
\small
\begin{tabular}{lccccc}
\hline\hline
%&&&&& \\[-8pt]
Observatory & $\overline{T_{\rm eff}}$ [K] & $\overline{\log{g}}$  [dex] & $\overline{\log{n_{{\rm He}}/n_{{\rm H}}}}$  [dex] & $\Delta T_{\rm eff}$ [K] & $\Delta\log{g}$ [dex]
\\ 
\hline
Steward & 31999.9 $\pm$ 17.3 & 5.262 $\pm$ 0.004 & --2.59 $\pm$ 0.005 & 873.7 $\pm$ 16.5 & 0.078 $\pm$ 0.003\\ 
NOT     & 31927.9 $\pm$ 27.1 & 5.299 $\pm$ 0.004 & --2.58 $\pm$ 0.007 & 840.9 $\pm$ 26.0 & 0.079 $\pm$ 0.004\\ 
SSO     & 32426.8 $\pm$ 67.7 & 5.260 $\pm$ 0.011 & --2.46 $\pm$ 0.015 & 808.9 $\pm$ 64.9 & 0.082 $\pm$ 0.010\\ 
ESO     & 31437.7 $\pm$ 31.5 & 5.224 $\pm$ 0.008 & --2.58 $\pm$ 0.011 & 793.7 $\pm$ 30.2 & 0.054 $\pm$ 0.008\\ 
\hline
\end{tabular}
\end{table}