Observations for the DESI Legacy Imaging Surveys began in August 2014. For each of the Legacy Surveys (BASS, DECaLS and MzLS) each position in the sky (minus some small filling factor) was designed to be observed in three "passes" in each of three filters (\(g\), \(r\), \(z\)). The passes were observed according to the following criteria:
| Pass | Conditions |
|---|---|
| 1 | Photometric and seeing < 1.3 arcsec |
| 2 | (Photometric and seeing < 2.0 arcsec) OR (seeing < 1.3 arcsec) OR (all Pass 1 tiles completed) |
| 3 | Unphotometric OR seeing > 1.3 arc sec |
MzLS and BASS mostly observed regions at Dec ≥ 32° whereas DECaLS mostly observed regions at Dec ≤ 32°. MzLS observed solely in \(z\), BASS observed in \(g\) and \(r\), and DECaLS observed in all 3 filters.
In addition to observations carried out as part of the DESI Legacy Imaging Surveys, data releases include reductions of data from other programs in (\(g\), \(r\), \(z\)) that overlap the footprint of the Legacy Surveys.
The figures below depict the (\(g\), \(r\), \(z\)) status of the DESI Legacy Imaging Surveys as of Data Release 9 (DR9). The coverage is color-coded by (extinction-corrected) depth. The solid line depicts the Galactic plane.
