\begin{table}%t2
%\centering
\par
\caption{Table of the instrument-specific characteristics.
\label{ta:ins}}
$$
\begin{tabular}{l@{\hspace{0.cm}}lr@{\hspace{0.3cm}\hspace{0.cm}}lr@{\hspace{0.cm}$~\pm~$\hspace{0.cm}}lr@{\hspace{0.cm}$~\pm~$\hspace{0.cm}}l}
\hline\hline
  \multicolumn{2}{l}{ } 
& \multicolumn{2}{c}{ HARPS} & \multicolumn{2}{c}{UCLES} & \multicolumn{2}{c}{CORALIE} \\
\hline
$N_{\rm meas}$ & & \multicolumn{2}{c}{86} & \multicolumn{2}{c}{45} & \multicolumn{2}{c}{39}\\
%\hline
$\delta\gamma$  &[km~s$^{-1}$] & 0.0 & ref. & 9.3306 & 0.0008 & 0.03366 & 0.0010\\
%\hline
$\sigma \rm (O{-}C)$\hspace{.25cm}  & [m~s$^{-1}$] & \multicolumn{2}{c}{1.41} & \multicolumn{2}{c}{3.34} & \multicolumn{2}{c}{6.01}\\
\hline
\end{tabular}
$$
\end{table}