\begin{table}%t1
\caption{\label{log}Observation log for GRB~090426.} 
\small%\centerline
{
\begin{tabular}{cccccccc} \hline\hline
\noalign{\smallskip}
Mean time          &  Exposure time             & Time since GRB~&    Seeing &  Instrument       &  Magnitude$^1$     & Filter       &   Comments  \\
(UT)                     &  (s)                                   & (days)                 & (\arcsec)  &                             &                                    & Grism     &	        \\ 
\hline
2009 Apr.   26.97190 &  $ 4 \times 120$	   &  0.43802	   & 1.4       & TNG/DOLORES	& $22.05 \pm 0.08$   & $B$         & AG detection   \\
2009 Apr.   26.97679 &  $ 2 \times 120$	   &  0.44291	   & 1.4       & TNG/DOLORES	& $21.69 \pm 0.07$   & $V$         & AG detection   \\
2009 Apr.   26.98818 &  $ 1 \times 180$	   &  0.45430	   & 1.4       & TNG/DOLORES	& $21.38 \pm 0.06$   & $R$        & AG detection   \\
2009 Apr.   26.99583 &  $ 1 \times 180$	   &  0.46195	   & 1.4       & TNG/DOLORES	& $21.25 \pm 0.09$   & $I$          & AG detection   \\ 
\hline
2009 Apr.   26.98457 &  $ 2 \times 1800$	   &  0.45069	   & 1.4       & TNG/DOLORES	& $-$		          & $LR-B$  & AG spectra     \\ 
\hline
2009 May  02.04516 &  $16 \times 120$	   &   5.51128	   & 1.4       & TNG/DOLORES	& $23.54 \pm 0.16$   & $R$        & HG detection   \\
2009 May  13.05282 &  $30 \times 180$	   &  16.51894	   & 1.0       & TNG/DOLORES	& $23.70 \pm 0.12$   & $R$        & HG detection   \\
2009 May  18.97929 &  $20 \times 180$	   &  22.44541	   & 1.0       & TNG/DOLORES	& $> 24.0$	          & $I$          & $3\sigma$ u.l. \\ 
\hline
2009 May  31.20833 &  $21\times 180$       &  35.67445      & 0.9        & LBT/LBC\_blue     & $24.11 \pm 0.10$  & $g'$        & HG + knot \\
2009 May  31.21875 &  $17\times 180$       &  35.68487      & 1.1        & LBT/LBC\_blue     & $23.83 \pm 0.13$  & $r'$         & HG + knot \\
2009 May  31.20833 &  $16\times 180$       &  35.67445      & 0.7        & LBT/LBC\_red       & $24.06 \pm 0.18$  & $i'$         & HG + knot  \\
2009 May  31.21875 &  $12\times 180$       &  35.68487      & 0.8        & LBT/LBC\_red       & $23.32 \pm 0.15$  & $z'$        & HG + knot  \\ 
\hline
2009 May  31.20833 &  $21\times 180$       &  35.67445      & 0.9        & LBT/LBC\_blue     & $24.70 \pm 0.10$  & $g'$        & HG  \\
2009 May  31.21875 &  $17\times 180$       &  35.68487      & 1.1        & LBT/LBC\_blue     & $23.86 \pm 0.07$  & $r'$         & HG  \\
2009 May  31.20833 &  $16\times 180$       &  35.67445      & 0.7        & LBT/LBC\_red       & $24.15 \pm 0.13$  & $i'$         & HG  \\
2009 May  31.21875 &  $12\times 180$       &  35.68487      & 0.8        & LBT/LBC\_red       & $23.73 \pm 0.13$  & $z'$        & HG  \\ 
\hline
2009 May  31.20833 &  $21\times 180$       &  35.67445      & 0.9        & LBT/LBC\_blue     & $25.46 \pm 0.20$  & $g'$        & N-E knot \\
2009 May  31.21875 &  $17\times 180$       &  35.68487      & 1.1        & LBT/LBC\_blue     & $24.72 \pm 0.15$  & $r'$         & N-E knot \\
2009 May  31.20833 &  $16\times 180$       &  35.67445      & 0.7        & LBT/LBC\_red       & $25.53 \pm 0.32$  & $i'$         & N-E knot \\
2009 May  31.21875 &  $12\times 180$       &  35.68487      & 0.8        & LBT/LBC\_red       & $24.87 \pm 0.29$  & $z'$        & N-E knot \\ 
\hline
\end{tabular}}
\smallskip
$^1$ Magnitudes are in the AB system and are not corrected for
Galactic extinction ($E(B-V)= 0.02$~mag \citealt{Schlegel98}). Point spread function (PSF) and aperture
photometry were performed, on both the afterglow and the host galaxy respectively, by using the 
{\it Daophot II} within the ESO-MIDAS package, the task Phot/Apphot within the IRAF 
package and the SExtractor package (\citealt{sex96}). In particular, an aperture radius of~2.2$''$ was adopted 
to cover the entire extended object observed in the LBT images. The calibration  of TNG data was performed 
using Landolt standard stars.  The calibration of LBT was done against the SLOAN catalogue. Errors and upper 
limits are given at $1\sigma$ confidence level. 
\end{table}