The Beijing-Arizona Sky Survey (BASS) covers ~5000 deg² in the g, r bands to depths of g=24.4, r=23.9.
The ninth data release (DR9) covers the full footprint of BASS (~5000 deg2) in g-band and r-band. DR9-north includes BASS images taken from 12th November 2015 through 7th March 2019.
The observations are taken with 90Prime on the Bok telescope in three passes at each sky location, and in each filter (g, r). "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).
Unique area is resolved by including the BASS and MzLS images (from DR9-north) if they are both at Declination > 32.375° and north of the Galactic Plane. Otherwise, the DECam images (from DR9-south) are used. This method eliminates the overlap when combining the North and South areas into the full DR9 footprint.