4 Errors

The errors of the measurements were determined as described in Sect. 4.2 of Paper I. The total internal errors of the positions presented in Table 1 were determined using the same relations given in Sect. 4.1 of Paper I.

Although it was predictable that the error of the Hipparcos Catalogue would be negligible compared to the errors of the measurements, we nevertheless did not use mean values for $\epsilon _{\rm c}(\alpha)$ and $\epsilon_{\rm c}(\delta)$ and calculated the error contribution of this catalogue on a zonal basis. It was determined that $\epsilon _{\rm c}(\alpha)$ varied between 1.9 and 9.7 mas and that $\epsilon_{\rm c}(\delta)$ varied between 2.2 and 7.1 mas.