\begin{table}%t1
\caption{Summary of the radio observations.}
\small%\centerline
{
\begin{tabular}{lcccclccc}
\hline\hline\noalign{\smallskip} 
Telescope & RA$_{\rm J2000}$& Dec$_{\rm J2000}$  & Observation  & $\nu$ & $\Delta \nu$  & $t$  & {\it {\it HPBW}}, PA  &   rms      \\ 
          & (h, m, s)  & ($^\circ$, $^{\prime}$, $^{\prime \prime}$)  &  date    &  ~MHz      & ~MHz          &  min       & (full array , ``$\times$'', $^{\circ}$)&   $\mu$Jy b$^{-1}$\\
\noalign{\smallskip}
\hline\noalign{\smallskip}
GMRT       & 04 54 09.00 & $-$10 14 19.0 & Nov. 06 & 327    &  16$\diamond$ &  330  & 10.6 $\times$ 9.6, $-$19   & 90--100$*$\\
VLA--BnA   & 04 54 16.28 & $-$10 16 05.9 & Jun. 06 & 4860   &  50  & 110   & 1.0 $\times$ 0.8, $-$68 & 10  \\	
VLA--CnB   & 04 54 16.28 &$-$10 16 05.9& Oct. 06 & 4860   &  50  &  60   & 4.0 $\times$ 2.0, $-$82 & 15   \\
VLA--BnA   & 04 54 16.28 & $-$10 16 05.9& Jun. 06 & 8430   &  50  &  170  & 0.6 $\times$ 0.5, 82      &  8 \\  
 \hline 
\end{tabular}}
\smallskip
$\diamond$ The observations were performed using a total bandwidth 
of 32~MHz (USB+LSB), but only the USB dataset was used for the analysis 
(see Sect.~2.1). \\
$*$ The rms noise level in the region of the relic is $\sim$90~$\mu$Jy b$^{-1}$, 
and increases up to $\sim$100~$\mu$Jy~b$^{-1}$ in the outer parts of the A~521 
field due to the presence of strong radio sources.
\label{tab:obs}
\end{table}