\begin{table}%t5
%\centering
\par
\caption{\label{opteff}Optical efficiencies (in \%) obtained from the various calibration
campaigns (\cite{catalano}).}
\begin{tabular}{c}
\hline\hline
\noalign{\smallskip}
Polarised channels: 2 detectors per PSB (a and b)\\
\hline
\begin{tabular}{c|c c c c|c|c} 
&{\bf100-1}&{\bf100-2}&{\bf100-3}&{\bf100-4}&{\bf Av.}&$\sigma$\\
Det a&24.6&38.8&33.1&32.8&&\\
Det b&32.8&39.8&28.7&26.7&32.2&4.1\\
\hline
&{\bf143-1}&{\bf143-2}&{\bf143-3}&{\bf143-4}&{\bf Av.}&$\sigma$\\
Det a&42.9&42.9&53.0&40.1&&\\
Det b&38.5&44.1&46.7&37.4&43.2&3.55\\
\hline
&{\bf217-5}&{\bf217-6}&{\bf217-7}&{\bf217-8}&{\bf Av.}&$\sigma$\\
Det a&33.5&28.9&28.2&34.2&&\\
Det b&33.8&31.3&26.2&34.6&31.3&2.7\\
\hline
&{\bf353-3}&{\bf353-4}&{\bf353-5}&{\bf353-6}&{\bf Av.}&$\sigma$\\
Det a&22.0&21.1&24.2&16.2&&\\
Det b&25.9&22.6&23.1&15.6&21.3&2.8\\
\end{tabular}\\
\hline
Total intensity channels\\
\hline
\begin{tabular}{c c c c|c|c} 
{\bf143-5}&{\bf143-6}&{\bf143-7}&{\bf143-8}&{\bf Av.}&$\sigma$\\
27.9&31.2&29.1&26.6&28.7&1.5\\
{\bf217-1}&{\bf217-2}&{\bf217-3}&{\bf217-4}&{\bf Av.}&$\sigma$\\
25.0&27.8&24.6&25.2&25.7&1.1\\
{\bf353-1}&{\bf353-2}&{\bf353-7}&{\bf353-8}&{\bf Av.}&$\sigma$\\
26.2&32.0&16.8&18.4&23.4&5.8\\
{\bf545-1}&{\bf545-2}&{\bf545-3}&{\bf545-4}&{\bf Av.}&$\sigma$\\
16.0&18.1&13.9&14.6&15.7&1.4\\
{\bf857-1}&{\bf857-2}&{\bf857-3}&{\bf857-4}&{\bf Av.}&$\sigma$\\
13.3&14.1&16.1&8.7&13.1&2.2\\
\end{tabular}\\
\hline
\end{tabular}
\tablefoot{Averages and standard deviations $\sigma$ are calculated per channel type (Polarised/total intensity $-$ Frequency). These results represent the best knowledge at present and caveats are explained in the corresponding section.}
\end{table}