(1) Observatoire de Paris, 61, Avenue de l'Observatoire, 75014 Paris
(2) Astronomical Inst. of the Academy of Sciences of the Czech Republic,
Bocni II 1401, 14131 Praha 4, Czech Rep.
The celestial pole offsets (CPO) in provisional HIPPARCOS reference frame was determined from the optical astrometry observations since 1899.7 till 1992.0. Into the solution entered more than 3.5 million observations from 46 instruments at 30 observatories. The amplitudes of the principal terms of nutation in longitude and obliquity following from the CPO are discussed and compared with the amplitudes derived from VLBI observations since 1981 till 1994 (Souchay et al. 1995, A&A 299).