\begin{table}  %t3
 \caption{Proper motion computed for each knot within the jet.}
   \label{tab:MP}
   \begin{tabular}{lccccccc}
   \hline
   \hline
   $\Delta t$ & Feature    & displacement $\rm H_{\rm \alpha}$ & displacement [SII] & $v$@150 pc $\rm H_{\rm \alpha}$ & $v$@150 pc [SII] & $v$ error & Comment \\
     yr & & arcsec & arcsec & km~s$^{-1}$ & km~s$^{-1}$ & km~s$^{-1}$ &     \\
   \hline
   1998--1996 & D       & 0.24 & 0.28 & 80 & 94 & 34 &center$^a$ \\
   1998--1996 & D$_{2}$ & 0.35 & 0.46 & 119 & 156& 34 & center \\
   1998--1996 & E       & 0.38 & 0.46 & 128 & 156 & 34 &center \\
   1998--1996 & F       & 0.39 & 0.28 & 131 & 95 & 34 &max$^b$ \\
   1998--1996 & F$_{2}$ & 0.75 & 0.93 & 252  & 316 & 34 &max \\
   \hline
   2005--1996 & D       & 1.34 & 1.54  & 106 & 123 & 8 &center \\
   2005--1996 & D$_{2}$ & --    & --    & --     & --      & -- & disappeared in 2005 \\
   2005--1996 & E       & --    & --    & --     & --      & -- & disappeared in 2005\\
   2005--1996 & F       & 0.24 & 0.74 & 19 & 59 & 8 & max \\
   2005--1996 & F$_{2}$ & 0.76 & 1.19 & 60 & 94 & 8 & max \\
   \hline
   \noalign{\smallskip}
   \multicolumn{6}{l}{$^a$ Proper motion computed using the position of the center of the contour.} \\
   \multicolumn{6}{l}{$^b$ Proper motion computed using the position of the maximum within the contour.} \\
   \end{tabular}
   \end{table}