Photometric Cross-Calibration Of The Sdss Stripe 82 Standard Stars Catalogue With Gaia Edr3, And Comparison With Pan-Starrs1, Des, Cfis, And Galex Catalogues

We extend the SDSS Stripe 82 Standard Stars catalogue with post-2007 SDSS imaging data. This improved version lists averaged SDSS ugriz photometry for nearly a million stars brighter than r similar to 22 mag. With 2-3 times more measurements per star, random errors are 1.4-1.7 times smaller than in the original catalogue, and about three times smaller than for individual SDSS runs. Random errors in the new catalogue are less than or similar to 0.01 mag for stars brighter than 20.0, 21.0, 21.0, 20.5, and 19.0mag in u, g, r, i, and z-bands, respectively. We achieve this error threshold by using the Gaia Early Data Release 3 (EDR3) Gmag photometry to derive grey photometric zeropoint corrections, as functions of RA and Declination, for the SDSS catalogue, and use the Gaia BP-RP colour to derive corrections in the ugiz bands, relative to the r-band. The quality of the recalibrated photometry, tested against Pan-STARRS1, DES, CFIS, and GALEX surveys, indicates spatial variations of photometric zeropoints <= 0.01 mag (rms), with typical values of 3-7 millimag in the RA, and 1-2 millimag in the Declination directions, except for less than or similar to 6millimag scatter in the u-band. We also report a few minor photometric problems with other surveys considered here, including a magnitude-dependent similar to 0.01 mag bias between 16 <= G(Gaia) <= 20 in the Gaia EDR3. Our new, publicly available catalogue offers robust calibration of ugriz photometry below 1 per cent level, and will be helpful during the commissioning of the Vera C. Rubin Observatory Legacy Survey of Space and Time.