\begin{table} %t2
      \caption{Spectral log.}
         \label{spectra}
%\centerline
{
\begin{tabular}{lllll}
\hline
\hline
    Slit centers &  & Total exposure &  Slit and aperture\\
\hline
     $\alpha$ & $\delta$ & time (s) &  positions \\
\hline
18\h01\m38\s & $-$23\degr10\arcmin16\arcsec   & 7800 (2$^a$) & I , [$-$160\arcsec, 24\arcsec]$^b$  \\
\hline
18\h00\m44\s & $-$23\degr37\arcmin12\arcsec   & 3900 (1$^a$) & II , [8\arcsec, 26\arcsec]$^b$ \\
\hline
17\h59\m41\s & $-$23\degr12\arcmin57\arcsec   & 7200 (2$^a$) & III , [$-$92\arcsec, 31\arcsec]$^b$ \\
\hline
18\h00\m04\s & $-$23\degr17\arcmin29\arcsec   & 7200 (2$^a$) & IV  , [$-$153\arcsec, 24\arcsec]$^b$ \\
            &                         &                    & IVa , [$-$32\arcsec, 22\arcsec]$^b$ \\    
\hline
18\h00\m59\s & $-$23\degr22\arcmin10\arcsec   & 7200 (2$^a$) & V , [$-$91\arcsec, 41\arcsec]$^b$ \\
            &                         &                    &  Va , [97\arcsec, 17\arcsec]$^b$ \\
\hline
\end{tabular}}
\smallskip
${^a}$ Number of individual frames. \\\
${^b}$ Spatial offset from slit center and extracted aperture length, both in arcsec.
   \end{table}