4 Summary

Our redshift catalogue is submitted jointly in a companion paper (Durret et al. 1999). Together with the catalogues presented here, it will be used to give an interpretation of the optical properties of Abell 496 (Durret et al. in preparation), in relation with the X-ray properties of this cluster (Pislar 1998).

Acknowledgements

We are very grateful to the MAMA team at Observatoire de Paris for help when scanning the photographic plate, and to Cláudia Mendes de Oliveira for her cheerful assistance at the telescope. The help of Françoise Warin in the data reduction is gratefully acknowledged. We thank the referee, John Huchra, for many comments which allowed us to improve the paper and in particular for pointing out mistakes which led us to redo the photometrical calibration. C.L. acknowledges financial support by the CNAA (Italia) fellowship reference D.D. No. 37 08/10/1997.

Figure 6: Difference between the R band CCD magnitude and the R band magnitude calculated from the photographic $b_{\rm J}$ magnitude (see text) as a function of observed R band CCD magnitude