\begin{table}%t3
\caption{\label{T:OB}Photometric constraints for OB stars.}     
%\centering
                          % used for centering table
\begin{tabular}{c   c   c }        % centered columns (4 columns)
\hline\hline                 % inserts double horizontal lines
Parameter & Min & Max \\    % table heading 
\hline                        
$V$          &   16 &   24 \\
$Q$-parm     & --2.0 & --0.4 \\
$U-B$        & --2.0 &  2.0 \\
$B-V$        & --0.5 &  2.0 \\
\hline                        
\end{tabular}
\end{table}