Legacy Survey - BASS

The Beijing-Arizona Sky Survey (BASS) will cover ~5000 deg² in the g, r bands to depths of g=24.4, r=23.9.

Current Status

The fourth data release (DR4) will include a portion of BASS, covering a disjoint footprint with ~3000 deg² in g-band, and ~2900 deg² in r-band.


The observations are taken with 90Prime on the Bok telescope in three passes at each sky location, and in each filter (z). "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.

In the g-band, single exposures reach 5-sigma point source depth of 23.92 (pass 1), 23.89 (pass 2), and 23.89 (pass 3). In the r-band, single exposures reach depths of 23.30 (pass 1), 23.30 (pass 2), and 23.18 (pass 3).