The orbits of open clusters in the Galaxy
  We present and analyze kinematics and orbits for a sample of 488 open
clusters in the Galaxy. The velocity ellipsoid for our present sample is
derived as ($\sigma_{U}$, $\sigma_{V}$, $\sigma_{W})$=$(28.7$, 15.8, 11.0) km
s$^{-1}$ which represents a young thin disc population. We also confirm that
the velocity dispersions increase with the age of cluster subsample. The orbits
of open clusters are calculated with three Galactic gravitational potential
models. The errors of orbital parameters are also calculated considering the
intrinsic variation of the orbital parameters and the effects of observational
uncertainties. The observational uncertainties dominate the errors of derived
orbital parameters. The vertical motions of clusters calculated using different
Galactic disc models are rather different. The observed radial metallicity
gradient of clusters is derived with a slope of $b=-0.070\pm0.011$ dex
kpc$^{-1}$. The radial metallicity gradient of clusters based on their
apogalactic distances is also derived with a slope of $b=-0.082\pm0.014$ dex
kpc$^{-1}$. The distribution of derived orbital eccentricities for open
clusters is very similar to the one derived for the field population of dwarfs
and giants in the thin disc.
