\begin{table}%t2
\caption{\label{Tab_2}Wavelength calibration using umbral Stokes \textit{V} profiles.}
%\centerline
 {
\begin{tabular}{ccccc}
\hline
\hline\\[-3.2mm]
{Name} & \multicolumn{2}{c}{CBS [m s$^{-1}$]} & \multicolumn{2}{c}{rms$^a$ [m s$^{-1}$]}\\
{} & {Fe~I~630.15} & {Fe~I~630.25} & {Fe~I~630.15} & {Fe~I~630.25}\\
\hline
{Spot~A} & {--231}& {--296} & {93} & {83}\\
{Spot~B} & {--245}& {--315} & {94} & {82}\\
{Spot~C} & {--201}& {--295} & {100} & {92}\\
{Spot~D} & {--231}& {--344} &  {147} & {107}\\
\hline
\end{tabular}}
\medskip
\par
$^a$ These values represent the variation of the center position of umbral Stokes \textit{V} profiles with $|\delta a |< 0.01$. 
\end{table}