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Radio-Optical Reference Frame Link Using the U.S. Naval Observatory Astrograph and Deep CCD Imaging

Zacharias, N.; Zacharias, M. I.

Between 1997 and 2004 several observing runs were conducted, mainly with the CTIO 0.9 m, to image International Celestial Reference Frame (ICRF) counterparts (mostly QSOs) in order to determine accurate optical positions. Contemporary to these deep CCD images, the same fields were observed with the U.S. Naval Observatory astrograph in the same ban…