0.5$ mag in $R$ and $I$, respectively. These represent $\sim 5\sigma$ deviations, probably indicative of the (lower) accuracy that can be achieved by subtraction of the images of the core in ground-based images of . Table 3 shows the flux ratios A1/A2, (A1$+$A2)/B and C/B for both of our pass bands, $R$ and $I$. Our ratios are consistent with those of SM93, comparing their $I'$ band with our $I$, and also with those of AVHM94 in both $R$ and $I$.

We estimated the apparent brightness of the longer part of the arc with a polygonal aperture containing its emission, save for a PSF avoidance zone 10 pixels in radius from the centers of brightness of the images of the core, which excluded any significant light in the PSF wings. We could not obtain a useful estimate of the apparent brightness of the shorter portion of the arc between A1 and A2, because the separation A1$-$A2 is too small to yield magnitudes for the arc without severe contamination. We used IRAF to lay out a polygonal aperture along a $\sim 1''$ length of the arc between images B and A2, thus minimizing contamination by A1, A2 and B. We calculated $R$ 