\begin{table}%t1
\caption{\label{table:1}Position shifts in $\mu$as assuming various values of $\beta$, for a source with measured  core-shift between $\nu_1$~= 2.3~GHz and $\nu_2$~= 8.4~GHz of $440~\mu$as, the median value found by Kovalev et~al. (\cite{Kova08}).}
\small%\centerline
 {
\begin{tabular}{rrrrrr}
\hline\hline
$\beta$ & $\Delta${\vec x}$_{2.3}$ & $\Delta${\vec x}$_{8.4}$ & (1-$\beta$)$\Delta${\vec x}$_{8.4}$ & $\Delta ${\vec x}$_{\rm ion}$ & $\Delta${\vec x}$_{\rm phase-delay}$\\
\hline
0.2 & 1928 & 1488 & 1190 & 29 & 326 \\
0.4 & 1088 & 648 & 389 & 21 & 281 \\
0.6 & 814 & 374 & 150 & 14 & 239 \\
0.8 & 682 & 242 & 48 & 7 & 201 \\
1.0 & 606 & 166 & 0 & 0 & 166 \\
1.2 & 558 & 118 & --24 & --7 & 134 \\
1.4 & 526 & 86 & --34 & --14 & 106 \\
1.6 & 503 & 63 & --38 & --21 & 80 \\
1.8 & 487 & 47 & --38 & --29 & 57 \\
2.0 & 476 & 36 & --36 & --36 & 36 \\
\hline
\end{tabular}}
\medskip
Notes: Cols.~2 and~3 give the deduced shifts from the jet base {\vec x}$_0$ at 2.3 and 8.4~GHz; Col.~4 the ``reduced'' group-delay shift at 8.4~GHz; Col.~5 the ``ionospheric'' shift; Col.~6 the total difference between positions measured at 8.4~GHz using interferometer phase, and ionosphere-corrected group delays.
\end{table}