The flux scales agree very well over 3 orders of magnitude in brightness. For bright sources, the accuracy of the flux density determinations are limited by systematic effects. Analysis of multiply observed sources has revealed that in a few percent of all fields, systematic flux calibration errors produce a larger offset in the flux scale. The uncertainty is elliptical for elliptical sources. Systematic astrometric errors are less than .
Larger objects have somewhat more accurate sizes.
An empirical estimate of the uncertainty as a function of flux density and size is where is the RMS uncertainty in the fitted size .