The Mayall z-band Legacy Survey (MzLS) will cover ~5000 deg² in the z band to depth of z=23.0.
The fourth data release (DR4) will include a portion of MzLS, covering a disjoint footprint with ~3000 deg² with at least one pass (including ~2500 deg² with two passes, and ~950 deg² with three passes).
The observations are taken with MOSAIC on the Mayall telescope in three passes at each sky location. "Pass 1" is observed in photometric, good-seeing conditions. "Pass 2" and "Pass 3" are observed in progressively worse conditions. This strategy was adopted to ensure a photometric solution across the full survey area. The observing time is adjusted as a function of sky brightness and transparency.
Single exposures reach 5-sigma point source depth of 23.04 (pass 1), 22.95 (pass 2), and 22.85 (pass 3).