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Astron. Astrophys. 318, 653-656 (1997)

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Correction to the precession constant from optical observations of extragalactic sources

Xu Tongqi , Lu Peizhen and Wang Shuhe

Shanghai Observatory, Academia Sinica, 200030 Shanghai, PR China

Received 23 August 1995 / Accepted 13 April 1996


The rediscussion of the precession constant was performed by optical observations of the counterparts of extragalactic radio sources with longer observational intervals. After a reduction of the optical catalogue systems, the fictitious 'proper motions' of extragalactic radio sources were obtained in the FK5 system. On the assumption that these fictitious 'proper motions' of extragalactic sources are the reflection of an incorrcet value of the precession constant, then the correction of precession constant can be estimated. The corrections are [FORMULA] for 43 sources and [FORMULA] for 24 sources, respectively. If the improvement of the 18.6-year nutation term is considered in the data processing, the corrections of the precession constant are [FORMULA] and [FORMULA], respectively. The results were also compared with those from VLBI.

Key words: astrometry – reference systems – radio continuum: galaxies

Send offprint requests to: Xu Tongqi

© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998