The CNOC Cluster Redshift Survey Catalogs. I. Observational Strategy and Data Reduction Techniques

We describe in detail the observational and data reduction techniques of a large redshift survey using multiobject spectroscopy designed to obtain ~2600 faint galaxy redshifts in fields of 16 rich clusters of galaxies with redshifts between 0. 2 and 0. 55. The primary goal of the survey is to establish whether the mass-to-light ratio of clusters rises with distance from the cluster center. To maximize multiplexing capability, we use ~1500 A wide band-limiting filters matched to the major features of spectra of galaxies at the cluster redshifts to allow for multitiering of spectra. Typically 80-110 spectra can be observed using a single slit mask. The area covered for each cluster ranges from about 1. 5 h₁00_^-1^ Mpc squared to 1. 5 h₁00_^-1^ Mpc x 6 h₁00_^-1^ Mpc. We describe the observing procedure, which involves real-time photometry and computer-based mask design and mask fabrication on site, allowing for the efficient use of telescope time. The spectroscopic data are extracted semiautomatically, and redshift measurement is performed using cross-correlation techniques. A detailed discussion of the determination of the completeness of the final redshift sample as functions of magnitude, color, geometric position, and redshift is also presented.