Legacy Survey - BASS

The Beijing-Arizona Sky Survey (BASS) will cover ~5000 degĀ² in the g, r bands to depths of g=24.4, r=23.9.

Current Status

The fourth data release (DR4) includes a portion of BASS, covering a footprint of ~3600 deg2 in either g-band or r-band (58,341 bricks with ~0.0623 deg2/brick). DR4 includes BASS images taken before July 13, 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 MzLS, there is not a perfect overlap between the footprints.


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).