\begin{table}%t2
\caption{\label{tab2}Coordinates (equinox: J2000) and 90\% confidence level errors
of the positions of the X-ray source 4U~1700+24 and of the optical star
HD~154791.}
\small%\centering
\par
\begin{tabular}{llllll}
\hline
\hline
\multicolumn{1}{c}{Source} & \multicolumn{1}{c}{RA} & \multicolumn{1}{c}{Dec} 
& \multicolumn{1}{c}{Error} & \multicolumn{1}{c}{Spacecraft} & 
\multicolumn{1}{c}{Reference}\\
 & \multicolumn{1}{c}{(J2000)} & \multicolumn{1}{c}{(J2000)} &  & 
\multicolumn{1}{c}{and instrument} & \\
\noalign{\smallskip}
\hline
\noalign{\smallskip}
\par
HD~154791  & 17$^{\rm h}$06$^{\rm m}$34$\fs$5183 & 
   +23$^{\circ}$58$'$18$\farcs$554 & 0$\farcs$014 & {\it Hipparcos} &
   Perryman et~al. (\cite{Perryman1997})\\
4U~1700+24 & 17$^{\rm h}$06$^{\rm m}$34$\fs$517  & 
   +23$^{\circ}$58$'$18$\farcs$66 & 0$\farcs$6     & {\it Chandra}/HRC~&
   this paper \\
4U~1700+24 & 17$^{\rm h}$06$^{\rm m}$34$\fs$6    & 
   +23$^{\circ}$58$'$14$\farcs$0 & 2$\farcs$1      & {\it ROSAT}/HRI &
   Morgan \& Garcia (\cite{Morgan2001}) \\
4U~1700+24 & 17$^{\rm h}$06$^{\rm m}$34$\fs$6    & 
   +23$^{\circ}$58$'$17$\farcs$3 & 3$\farcs$5      & {\it ROSAT}/PSPC &
   Morgan \& Garcia (\cite{Morgan2001}) \\
4U~1700+24 & 17$^{\rm h}$06$^{\rm m}$34$\fs$56   & 
   +23$^{\circ}$58$'$18$\farcs$7 & 4$''$           & {\it XMM-Newton}/EPIC 
&
   this paper \\
\hline
\end{tabular}
\end{table}