Comparison of optical magnitudes of astrometric radio sources obtained from Gaia and ground based observations

In this paper, optical magnitudes of astrometric radio sources from the OCARS catalog measured with ground-based telescopes and by Gaia space telescope have been compared. It was found that for some sources these magnitudes agree well, while other sources show significant disagreement. The disagreement is mostly observed for extended Galaxies for which different image processing procedure is usually applied on ground-based and Gaia telescopes. Nevertheless, such a comparison can be useful as a method of verification of non-uniform or unreliable photometry data from the literature and for cross-identification of objects in various catalogs.