PHOTOCENTRE SHIFT IN COMET OBSERVATIONS

               A.V.Devyatkin, E.V.Kornilov

    Pulkovo Observatory, Saint Petersburg, 196140, Russia


     Position observation of comets have systematic errors due to
displasement of observed photocentre relatively centre of inertia, i. e.
photocentre shift. Its shift is caused by a comet and solar wind matter
interaction. His value can be somewhat one second of arc. To calculate
the photocentre shift we use a model of comet image in which the following
factors are taken into account:
- density and velocity of solar wind stream,
- mass production rate of comet nucleus and ejection velosity,
- Sun, comet and Earth configuration,
- measurement method of comet image.
Reduction taking into account a mentioned factors was obtained.