\begin{table}%t1 \caption{Details of the observations used for this work. $N$ is the number of exposures that were taken with a given detector integration time (DIT). NDIT denotes the number of integrations that were averaged online by the read-out electronics during the observation. The scale of all observed images is 0.027$^{\prime\prime}$ per pixel.} \label{TabObservations} %\centering \par \begin{tabular}{c c c c c c} \hline\hline Date & $\lambda_{\rm central}$ [$\mu$m] & $\Delta \lambda$ [$\mu$m] & $N$ & NDIT & DIT [s] \\ \hline 29 April 2006 & 1.66 & 0.33 & 31 & 28 & 2 \\ 09 July 2004 & 2.00 & 0.06 & 8 & 4 & 36 \\ 12 June 2004 & 2.06 & 0.06 & 96 & 1 & 30 \\ 12 June 2004 & 2.24 & 0.06 & 99 & 1 & 30 \\ 09 July 2004 & 2.27 & 0.06 & 8 & 4 & 36 \\ 09 July 2004 & 2.30 & 0.06 & 8 & 4 & 36 \\ 12 June 2004 & 2.33 & 0.06 & 99 & 1 & 30 \\ 09 July 2004 & 2.36 & 0.06 & 8 & 4 & 36 \\ \hline \end{tabular} \end{table}