\begin{table}%t5
\caption{Normalized Stokes parameters $q_B$ and $u_B$ for
   different limits of integration $\theta_0$; at FWHM, $3^{\circ}$
   and $20^{\circ}$. These parameters represent the optical spurious
   polarization introduced by PLANCK telescope optics for the studied
   focal plane configuration (in bold) and other study cases (see text).}
\label{tab:parameters}
%\centering
\par
\begin{tabular}{c c c c c c c c c c}
 \hline\hline
   {\bf 30 GHz}
   &\multicolumn{3}{c|}{Position 1}
   &\multicolumn{3}{c|}{Position 4}
   &\multicolumn{3}{c}{\bf{Position 27}}\\ \hline
   $\theta_0$
   &$0.5^{\circ}$&$3.0^{\circ}$&$20.0^{\circ}$
   &$0.5^{\circ}$&$3.0^{\circ}$&$20.0^{\circ}$
   &$\bf{0.5^{\circ}}$&$\bf{3.0^{\circ}}$&$\bf{20.0^{\circ}}$
   \\\hline
   $q_B$ (\%)
   & $-$0.0391 & $-$0.275 & $-$0.275
   &  1.79   &  3.17  &  3.10
   & \bf{$-$0.0057 }& \bf{$-$0.131} & \bf{$-$0.131} \\
   $u_B$ (\%)
   &  0.00365 &  0.00117 & 0.00110
   &  5.2     &  5.1     & 5.0
   & \bf{$-$0.427}   & \bf{$-$0.204}   & \bf{$-$0.205}\\\hline
\multicolumn{10}{c}{}\\
\hline\hline
   {\bf 100 GHz}
   &\multicolumn{3}{c|}{Position 1}
   &\multicolumn{3}{c|}{\bf{Position 4}}
   &\multicolumn{3}{c}{Position 27}\\ \hline
   $\theta_0$
   &$0.2^{\circ}$&$3.0^{\circ}$&$20.0^{\circ}$
   &$\bf{0.2^{\circ}}$&$\bf{3.0^{\circ}}$&$\bf{20.0^{\circ}}$
   &$0.2^{\circ}$&$3.0^{\circ}$&$20.0^{\circ}$
   \\\hline
   $q_B$ (\%)
   &  0.164 &  0.093  &  0.093
   & \bf{$-$0.138} & \bf{$-$0.0398} & \bf{$-$0.0422}
   &  1.42  &  2.05   &  2.05 \\
   $u_B$ (\%)
   & $-$0.00418 &  0.0052 &  0.0052
   & \bf{$-$0.51}    & \bf{$-$0.086}  & \bf{$-$0.086}
   &  2.22    &  3.44   &  3.43 \\\hline
 \end{tabular}
\end{table}