Meridian circle reductions using preliminary HIPPARCOS positions.
Abstract
New reductions of differential observations made by the Bordeaux and La Palma automatic meridian circles have been undertaken, replacing the positions of the FK5 reference stars by those in the Hipparcos 18-month intermediate solution. A remarkable improvement in the post-fit residuals of the classical least-squares adjustment is obtained for both instruments, with data covering several years. The residuals show small systematic waves corresponding to (as yet unexplained) instrumental errors. After correction of these errors, and after incorporating an improved modelling of the instrumental parameters, a new reduction of the Bordeaux observations has been made. We present a comparison of the resulting positions for 173 radio stars with the intermediate Hipparcos positions, indicating the ultimate accuracy that can be attained with automatic meridian circles. In the future these instruments, equipped with properly calibrated CCDs, should make an effective contribution in extending the Hipparcos reference frame to the range 11-16mag. This reference frame is represented by the 120000 Hipparcos stars and the one million Tycho stars, containing all stars on the sky brighter than 11.5mag.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- December 1995
- Bibcode:
- 1995A&A...304..121R
- Keywords:
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- ASTROMETRY;
- INSTRUMENTATION: MISCELLANEOUS