## 10. Results and conclusionsTable 3 shows our results for the rotation parameters for several selected values of , averaged over the ten groups. The stated errors reflect the dispersion between the different star groups. The corresponding results for the glide parameters are shown in Table 4. Table 5 shows the corresponding adjusted parameters for the proper motions. These latter parameters are much better behaved and an adjustment with without outliers elimination was enough to represent the differences. Fig. 4 shows the coefficients of the adjusted series, averaged on the ten star groups. These are the main results of our analysis.
Our analysis of the statistical properties of the series shows that
and
are enough to represent correctly
the difference fields for position and proper motions. As a check, we
compared the results with a vectorial analysis program by F. Mignard
(Mignard 1999), named Our results reveal the existence of several large distortions in
the SAO reference system positions, evidenced by large Fourier
coefficients of large order. The most important effects are in
declination, associated with a large displacement field towards the
South Pole (Fig. 3). Taking into account that the HIPPARCOS
reference frame, being a materialization of the ICRS, is essentially
free of these distortions, these zonal effects are due to the SAO
catalogue errors. The present series may correct the main systematic
effects. © European Southern Observatory (ESO) 2000 Online publication: July 13, 2000 |