\begin{table}%t1
\caption{\label{obspara}Observational parameters.}
\begin{tabular}{lll}
\hline\hline\noalign{\smallskip}
  System temperature & 22~K $T_{\rm a}$   \\
  $HPBW$         & $9\farcm5$   \\
  Subscan separation, sampling & 3$\arcmin$ \\
  Scan velocity  & 2\fdg5/min or 4\degr/min  \\
  Scan direction & $\ell$ and $b$    \\
  Typical rms-noise for $I$      &0.5--0.7~mK $T_{\rm B}$   \\
  Typical rms-noise for $U$ and $Q$      & 0.3--0.4~mK $T_{\rm B}$    \\
  Typical rms-noise for $PI$        & 0.3--0.5~mK $T_{\rm B}$     \\
  Central frequency   & 4800~MHz or 4963~MHz   \\
  Bandwidth & 600~MHz or 295~MHz    \\
  aperture efficiency            & 62\%         \\
  beam efficiency                & 67\%          \\
  $T_{\rm B}$/S                        & 0.164~K/Jy        \\
  Main Calibrator                 & 3C286       \\
  Flux density                    & 7.5~Jy \\
  Percentage Polarization         & 11.3\% \\
  Polarization Angle              & 33\degr \\
\hline
\end{tabular} 
\end{table}