1995A&AS..110..159B

In the goal to probe the distribution of galaxies at redshifts z≃0.1-0.5, we have started a deep redshift survey limited by R≤20.5. Using multiple object spectroscopy on the 2 largest telescopes at the European Southern Observatory, we have so far obtained 491 low-resolution spectra (∼10-20A FWHM) of faint galaxies. Among the 386 spectra of galaxies with R≤20.5, redshifts have been measured for 320 objects (81%). The spectra of 105 objects fainter than our catalogue limit (with R≥20.5) were also taken simultaneously and at no additionnal cost in observing time, and we derived redshifts for 47 of them (43%). In this article we describe the different methods which we are using to reduce the spectroscopic data in a homogeneous way. Because of the low signal-to-noise ratio of the spectra, each step of the reduction must be optimized. Various tests are presented to evaluate the quality of the reduced data, and the linearity and zero-point of the redshift scale are checked. Using the already available data, we present preliminary diagrams of the redshift distribution and the fraction of objects with emission-lines.