\begin{table}%t4
%\centering
\par
\caption{VLBA rms astrometric errors (in $\mu$as) for a relative source
separation $\delta -\delta _0= 1\degr$. Individual astrometric error contributions
from calibrator position, Earth orientation parameter, station coordinate, and 
dry and wet troposphere uncertainties are given separately, while the last
two lines indicate the total astrometric errors when all model parameters
are perturbed together.\label{VLBADC}}
%\centering
\par
\begin{tabular}{lcccccccccccccccccc}
\hline
\hline
\noalign {\vskip 1.0mm}
 &&\multicolumn{16}{c}{Declination of source}\\
\noalign {\vskip 0.5mm} \noalign {\vskip 1.0mm} \hfil
\hfil
&&\multicolumn{2}{c}{$-25\degr$}&&\multicolumn{2}{c}{$0\degr$}&&\multicolumn{2}{c}{$25\degr$}
        &&\multicolumn{2}{c}{$50\degr$}&&\multicolumn{2}{c}{$75\degr$}&&\multicolumn{2}{c}{$85\degr$}\\
\noalign {\vskip 1.0mm}
Error component     &&$\Delta\alpha\cos\delta \hfil$ &$\Delta\delta$ &&$\Delta\alpha\cos\delta \hfil$ &$\Delta\delta$&&
        $\Delta\alpha\cos\delta \hfil$&$\Delta\delta$&&$\Delta\alpha\cos\delta \hfil$&$\Delta\delta$&&
        $\Delta\alpha\cos\delta \hfil$&$\Delta\delta$&&$\Delta\alpha\cos\delta \hfil$&$\Delta\delta$\\
\noalign {\vskip 0.0mm}
\hline
Calibrator position (1~mas error)   &&   ~~7   &   ~~8   &&   ~1  &   ~~7 && ~8  &   11  &&   21  &   ~2  &&   59  &   ~2 && 199 & ~1 \\
Calibrator position (0.25~mas error) &&   ~~2   &   ~~7   &&   ~1  &   ~~3 && ~2  &   ~4  &&   ~5  &   ~2  &&   20  &   ~1 && ~43 & ~1\\
Earth orientation               &&   ~~5   &   ~~7   &&   ~5  &   ~~3 && ~5  &   ~4  &&   ~4  &   ~3  &&   ~3  &   ~1 && ~~3 & ~1 \\
Antenna position                &&   ~~2   &   ~~9   &&   ~2  &   ~~6 && ~2  &   ~5  &&   ~3  &   ~3  &&   ~2  &   ~2 && ~~2 & ~2 \\
Dry troposphere                 &&   ~17   &   ~54   &&   ~6  &   ~19 && ~2  &   12  &&   ~5  &   ~9  &&   11  &   ~9 && ~12 & 13 \\
Wet troposphere (mean)          &&   ~80   &   272   &&   32  &   ~98 && 11  &   41  &&   12  &   32  &&   43  &   41 && ~60 & 62 \\
Wet troposphere (max)           &&   112   &   358   &&   43  &   114 && 19  &   61  &&   17  &   46  &&   59  &   55 && ~74 & 71 \\
\hline
Total (mean wtrp)                &&   ~84   &   284   &&   30  &   ~99 && 16  &   42  &&   25  &   33  &&   81  &   36 && 189 & 67 \\
Total (max wtrp)                 &&   121   &   481   &&   44  &   134 && 20  &   56  &&   26  &   46  &&   92  &   65 && 212 & 74 \\
\hline
\end{tabular}
\end{table}