4 Conclusion

The precision of the declination system of SIPA1 catalog is as high as the best modern meridian circles, the right ascension system is degraded a little by a magnitude equation. If the problem of the magnitude equation in the photoelectric recording device can be resolved, the precision of right ascension observation will be improved significantly. The PHA I still can play important role in the maintenance of the Hipparcos proper motion system and in the improvement of the link between the Hipparcos and radio reference systems by long-term observation of radio stars.

Acknowledgements

The authors would like to give many thanks to the China National Natural Science Foundation, to the Bureau of Basic Research and Bureau of International Cooperation of the Chinese Academy of Sciences, and the China Astronomical Committee, which give great support to our research.