- ID:
- ivo://CDS.VizieR/J/other/Ser/182.35
- Title:
- Corrected proper motion for HIP stars
- Short Name:
- J/other/Ser/182.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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, Cat. <A HREF="http://cdsarc.u-strasbg.fr/cgi-bin/Cat?I/239">I/239</A>). We used these latitude data for the inverse investigations - to improve the proper motions in declination µ<SUB>δ</SUB> of the mentioned Hipparcos stars. We determined the corrections Δµ<SUB>δ</SUB> and investigated agreement of our µ<SUB>δ</SUB> and those from the catalogues Hipparcos and new Hipparcos (van Leeuwen 2007, Cat. <A HREF="http://cdsarc.u-strasbg.fr/cgi-bin/Cat?I/311">I/311</A>). 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 20mas 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 µ<SUB>δ</SUB> 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 µ<SUB>δ</SUB> 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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- ID:
- ivo://CDS.VizieR/J/other/Ser/177.109
- Title:
- Corrections to HIP proper motions
- Short Name:
- J/other/Ser/177.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the data on latitude variations obtained from observations with 10 classical photographic zenith tubes (PZT) in order to improve the Hipparcos proper motions in declinations µ<SUB>δ</SUB> for 807 stars. Part of observing programmes, carried out during the last century for the purpose of studying the Earth's rotation, were realized by using PZT instruments. These observations were performed within in the intervals (tens of years) much longer than that of the Hipparcos mission (less than 4 years). In addition, the annual number of observations for every PZT- programme star is several hundreds on the average. Though the accuracy of the star coordinates in the Hipparcos Catalogue is by two orders of magnitude better than that of the star coordinates from the PZT observations, the large number of observations performed a much longer time interval makes it possible to correct the Hipparcos proper motions and to improve their accuracy with respect to the accuracy given in the Hipparcos Catalogue. Long term examinations of latitude and time variations were used to form the Earth Orientation Catalogue (EOC-2), aimed at a more accurate determination of positions and proper motions for the stars included. Our method of calculating the corrections of the proper motions in declination from the latitude variations is different from the method used in obtaining the EOC-2 Catalogue. Comparing the results we have established a good agreement between our µ<SUB>δ</SUB> and the EOC-2 ones for the star sample used in the present paper.
