All Figures

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2852_fig1.ps} \end{figure}$ Figure 1: R-band image of SBS 1520+530 obtained on May 7, 2003. The quasar images, the reference stars S3 and S4, and the star we use for the PSF are labelled. The field size is $2.8~{\rm arcmin}\times3.5$ arcmin. The area marked with the box is shown in Fig. 2.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{2852_fig2.ps}} \end{figure}$ Figure 2: R-band zoom of the central part of SBS 1520+530. The field size is $30~{\rm arcsec}\times25$ arcsec. North is up and East is to the left. The bright foreground star next to the two quasar images A and B is saturated in the centre. S1 and S2 are also foreground stars. The lens galaxy ( $m_{R, {\rm gal}}\approx 21.6$ mag, Crampton et al. 1998) is too faint to be seen in this image.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8cm,clip]{2852_fig3.ps} \end{figure}$ Figure 3: R-band light curves of the two quasar images A and B in SBS 1520+530 and the reference star S4. For clarity the magnitude for image B was shifted by -0.4 mag, S4 was shifted by +2.4 mag. The dotted vertical line indicates the day with the Julian Date-2 452 000=880 when the mirror was cleaned. The dashed horizontal line shows the magnitude of the reference star S4 $m_{\rm S4}=15.76$ mag.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{2852_fig4.ps} \end{figure}$ Figure 4: V-R colour curve for the quasar images A ( top) and B ( bottom). The best-fitting value for each quasar image is plotted with a dashed line.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{2852_fig5.eps} %\end{figure}$ Figure 5: Probability p for time delays based on our SBS 1520+530 light curve. The probability was calculated from 10 000 Monte-Carlo realizations of the light curve, and by interpolating quasar A each time. 95 per cent of the probability is contained in the four separate regions above the dashed line.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{2852_fig6.ps} \end{figure}$ Figure 6: Top panel: R-band light curves of the two quasar images A (filled circles) and B (open circles). The B light curve has been shifted by -130 days, as indicated by the arrow, and by -0.83 mag. Bottom panels: difference light curve between the shifted and interpolated quasar images. This was calculated in both ways: by interpolating image A or by interpolating image B (see text).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8cm,clip]{2852_fig7.ps} \end{figure}$ Figure 7: Composite of the difference light curves based on our Maydanak data (filled circles, see Fig. 6) and the data published by Burud et al. (2002) (open circles, the linear trend determined by them is shown with a dashed line). In both cases image A was linearly interpolated.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{2852_fig1.ps} \end{figure}$	Figure 1: R-band image of SBS 1520+530 obtained on May 7, 2003. The quasar images, the reference stars S3 and S4, and the star we use for the PSF are labelled. The field size is $2.8~{\rm arcmin}\times3.5$ arcmin. The area marked with the box is shown in Fig. 2.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{2852_fig2.ps}} \end{figure}$	Figure 2: R-band zoom of the central part of SBS 1520+530. The field size is $30~{\rm arcsec}\times25$ arcsec. North is up and East is to the left. The bright foreground star next to the two quasar images A and B is saturated in the centre. S1 and S2 are also foreground stars. The lens galaxy ( $m_{R, {\rm gal}}\approx 21.6$ mag, Crampton et al. 1998) is too faint to be seen in this image.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{2852_fig4.ps} \end{figure}$	Figure 4: V-R colour curve for the quasar images A ( top) and B ( bottom). The best-fitting value for each quasar image is plotted with a dashed line.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{2852_fig5.eps} %\end{figure}$	Figure 5: Probability p for time delays based on our SBS 1520+530 light curve. The probability was calculated from 10 000 Monte-Carlo realizations of the light curve, and by interpolating quasar A each time. 95 per cent of the probability is contained in the four separate regions above the dashed line.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{2852_fig6.ps} \end{figure}$	Figure 6: Top panel: R-band light curves of the two quasar images A (filled circles) and B (open circles). The B light curve has been shifted by -130 days, as indicated by the arrow, and by -0.83 mag. Bottom panels: difference light curve between the shifted and interpolated quasar images. This was calculated in both ways: by interpolating image A or by interpolating image B (see text).
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$\begin{figure} \par\includegraphics[angle=-90,width=8cm,clip]{2852_fig7.ps} \end{figure}$	Figure 7: Composite of the difference light curves based on our Maydanak data (filled circles, see Fig. 6) and the data published by Burud et al. (2002) (open circles, the linear trend determined by them is shown with a dashed line). In both cases image A was linearly interpolated.
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