March 29, 2017
The Radio Optical Reference Frame
Optical Image Database (OID)
Presented here are preliminary results of an ongoing program to
obtain precise optical positions of the RORF sources. The radio frame,
defined by the positions of selected extragalactic radio sources, can
now be established to an accuracy of better than one milliarcsecond.
This defines a frame that is more accurate than the internal accuracy
of the HIPPARCOS catalog and far exceeds that of the Fifth Fundamental
Catalog (FK5). Because of the need to link these optical reference
frames to the radio, it is important to include in the radio catalog
objects that are detectable at both radio and optical wavelengths. In
this way, the accuracy of the optical catalogs can be improved,
including the proper motions.
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