CCD ASTROMETRY ORIENTED ANALYSIS OF DIGITIZED MULTIPLE IMAGES
(PLANETS, SATELLITES, ETC.) OBTAINED WITH THE PULKOVO PVC.

George Goncharov
Pulkovo observatory, Saint-Petersburg, 196140, Russia

   Some photographic fields with several images obtained by the
Pulkovo photographic vertical circle (PVC) in 1987-1995 were digitized
with pixel of 20 microns. The fields contain Jupiter with Galilean
satellites, outer planets with stars and multiple stars. As the
influence of the emulsion granularity and other photographic effects
on the instant coordinates of the images is less than 5 microns we can
consider some problems of both photographic and CCD astrometry.
   The turbulence in zenith of Pulkovo have mean amplitude of 0.7
arcsec with characteristic period of 10 seconds. The oscillations of
images in one field are correlated up to 60 - 90%. As the accuracy is
in proportion with the -1/4th power of exposure there is an optimal
exposure for differential observations with a CCD. It depends on
turbulence and now can be set up for every night apart. So, the
accounting of the co-turbulence provides differential coordinates of
similar images in one field with accuracy of 0.04 arcsec for the
exposure of 30 seconds.
   Various methods of image's centre determination are applied for
Jupiter and Galilean satellites, Polar star and its satellite and
other different objects in one field. The differential coordinates of
the objects separated by 7 magnitudes were determined within 0.08
arcsec.