Folks doing Sloan photometry will be interested to know that the Tonry et al (2018) ATLAS refcat2 is now accessible (query-able) through VizieR. This is an all-sky photometric catalogue providing g,r,i,z data for stars up to about mag 10 or so. The claim is that the global zero-point is reliable to ~0.005 mag, while star-by-star errors are about 0.015 - 0.030 mag. Some checking suggests the g,r,i data are quite good, while z --- often derived from remote passbands --- is somewhat squirrely. One must check the various flags on each data-entry to assess possible problems. The catalogue results from a combination of new and existing data, including the ATLAS Pathfinder telescope (similar to the APASS systems), revised SkyMapper DR1 data in the south, completely re-reduced APASS data taken from CTIO, and Pan-STARRS. Massaged GAIA DR2 and 2MASS data are also part of the mix. Tycho-2 and other sources have been used to derive gri for bright stars. The description and links are here:
https://cdsarc.unistra.fr/viz-bin/cat/J/ApJ/867/105
...and the source paper, definitely worth reading, is at:
https://ui.adsabs.harvard.edu/abs/2018ApJ...867..105T/abstract
\Brian