\begin{table}%t11
\caption{\label{t:r}$R'$ parameter as derived from both HST and ground based data (note the
different definition with respect to the usual $R$~parameter).}%The complete table is available at the~CDS.}
\par
%\centering
\par
\begin{tabular}{lcccc}
\hline\hline \noalign{\smallskip}
 NGC~/IC     & $R'$(HST)      & $R'$(ground based)& $\langle$$R'$$\rangle$     & $Y$($\langle$$R'$$\rangle$)     \\
\hline
  104 & 0.69 $\pm$ 0.07 & 0.68 $\pm$ 0.09 & 0.69 $\pm$ 0.07 & 0.253 $\pm$ 0.012 \\
  288 &               & 0.69 $\pm$ 0.14 & 0.69 $\pm$ 0.14 & 0.250 $\pm$ 0.024 \\
  362 & 0.75 $\pm$ 0.08 & 0.63 $\pm$ 0.15 & 0.75 $\pm$ 0.08 & 0.260 $\pm$ 0.012 \\
 1257 & 0.49 $\pm$ 0.14 &               & 0.49 $\pm$ 0.14 & 0.213 $\pm$ 0.024 \\
 1261 & 0.62 $\pm$ 0.10 & 0.69 $\pm$ 0.09 & 0.62 $\pm$ 0.10 & 0.238 $\pm$ 0.017 \\
\hline 						\end{tabular}						\tablefoot {The final adopted value $\langle$$R'$$\rangle$ is the weighted average between the two estimates, when available. $Y$($\langle$$R'$$\rangle$) is the corresponding He~\mbox{abundance}. {The complete table is available at the~CDS.}}\vspace*{-3mm}
\end{table}