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) includes a portion of MzLS, covering a footprint of ~3600 deg2 with at least one pass (57,943 bricks with ~0.0623 deg2/brick). DR4 includes MzLS images taken prior to June 6, 2016 over the Right Ascension (RA) range of 55 to 301 degrees, and Declination (Dec) range of +29 to +82 degrees. There are two small regions near RA,Dec = (56, +33) and RA,Dec = (66, +68), plus the main contiguous Northern Galactic Cap region, which lies within RA of 87 to 301 degrees. While the footprint area is about the same as that of BASS, there is not a perfect overlap between the footprints.
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).