During the last century, there were many so-called independent latitude (IL)
stations with the observations which were included into data of a few
international organizations (like Bureau International de l'Heure - BIH,
International Polar Motion Service - IPMS) and the Earth rotation programmes
for determining the Earth Orientation Parameters - EOP. Because of this,
nowadays, there are numerous astrometric ground-based observations (made over
many decades) of some stars included in the Hipparcos Catalogue (ESA 1997).
We used these latitude data for the inverse investigations - to improve the
proper motions in declination ?? of the mentioned Hipparcos stars. We
determined the corrections ??? and investigated agreement of our ?? and those
from the catalogues Hipparcos and new Hipparcos (van Leeuwen 2007). To do
this we used the latitude variations of 7 stations (Belgrade,
Blagoveschtschensk, Irkutsk, Poltava, Pulkovo, Warsaw and Mizusawa), covering
different intervals in the period 1904.7 - 1992.0, obtained with 6 visual and
1 floating zenith telescopes (Mizusawa). On the other hand, with regard that
about two decades have elapsed since the Hipparcos ESA mission observations
(the epoch of Hipparcos catalogue is 1991.25), the error of apparent places
of Hipparcos stars has increased by nearly 20 mas because of proper motion
errors. Also, the mission lasted less than four years which was not enough
for a sufficient accuracy of proper motions of some stars (such as double or
multiple ones). Our method of calculation, and the calculated ?? for the
common IL/Hipparcos stars are presented here. We constructed an IL catalogue
of 1200 stars: there are 707 stars in the first part (with at least 20 years
of IL observations) and 493 stars in the second one (less than 20 years). In
the case of ?? of IL stars observed at some stations (Blagoveschtschensk,
Irkutsk, Mizusawa, Poltava and Pulkovo) we find the formal errors less than
the corresponding Hipparcos ones and for some of them (stations
Blagoveschtschensk and Irkutsk) even less than the new Hipparcos ones.
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