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The Commission 19 (Earth Rotation) of the International Astronomical Union (IAU) established
the Working Group on Earth Rotation in the Hipparcos Reference Frame (WG ERHRF) at 1995
to collect the optical observations of latitude and universal time variations, made during 1899.7 – 1992.0
in line with Earth orientation programmes (to derive Earth Orientation Parameters – EOP), with Dr. Jan
Vondr´ak (Astronomical Institute of Academy of Sciences of the Czech Republic, Prague) as a head of WG
ERHRF. We participated in this international project with the Belgrade visual zenith – telescope (BLZ)
latitude data of the period 1949.0 – 1986.0, after new reduction of BLZ data made during my MSc thesis
finished 1997 at Natural – Mathematical Faculty of Belgrade University. Dr. Vond´ark collected 4.4 million
optical observations of latitude/universal time variations made at 33 observatories. The data were used for
EOP investigations, Hipparcos satellite Catalogue – radio sources connection, etc.
Nowadays, it is actual to correct the positions and proper motions of stars of Hipparcos Catalogue (as
an optical reference frame) using ground – based observations of some Hipparcos stars. In this PhD thesis
we use the latitude observations made by several types of classical astrometric instruments: visual (ZT) and
floating zenith – telescope (FZT), visual zenith tube (VZT) and photographic zenith tube (PZT); 26 different
instruments located at many observatories all over the world (used in the programmes of monitoring the Earth
orientation during the 20th century). We received the data from Dr. Vondr´ak via private communication.
The observatories and instruments are: International Latitude Service – ILS (Carloforte – CA ZT, Cincinnati
– CI ZT, Gaithersburg – GT ZT, Kitab – KZ ZT, Mizusawa – MZZ ZT, Tschardjui – TS ZT and Ukiah – UK
ZT), Belgrade (BLZ ZT), Blagoveschtschensk (BK ZT), Irkutsk (IRZ ZT), Poltava (POL ZT), Pulkovo (PU
and PUZ ZT), Varsovie (VJZ ZT), Mizusawa (MZL FZT), Tuorla – Turku (TT VZT), Mizusawa (MZP and
MZQ PZT), Mount Stromlo (MS PZT), Ondˇrejov (OJP PZT), Punta Indio (PIP PZT), Richmond (RCP
and RCQ PZT) and Washington (WA, W and WGQ PZT).
The task is to improve proper motions in declination of the observed Hipparcos stars. The original
method was developed, and it consists in removing from the instantaneous observed latitudes all known
effects (polar motion and some local instrumental errors). The corrected latitudes are then used to calculate
the corrections of Hipparcos proper motions in declination (Damljanovi´c, Serb. Astron. J. 170, 2005). The
Least Squares Method (LSM) is used with the linear model.
We compared calculated results with ARIHIP and EOC-2 data, and the consistency were good. The
newly obtained values of proper motions in declination are substantially more precise than those of the
Hipparcos Catalogue. It is because the time interval covered by latitude observations (tens of years) is much
longer than the Hipparcos one (less than four years), and because of great number of observations made
during this interval (Damljanovi´c et al., Serb. Astron. J. 172, 2006).
Our method is completely different from the one used to determine the catalogue EOC-2 (Vondr´ak,
Serb. Astron. J. 168, 2004). It was an almost independent check of the proper motions of EOC-2, also. The
catalogue EOC-2 is used in this thesis to distinguish the corrections of the two stars of a pair observed by
Horrebow – Talcott method. The difference between the two proper motions is constrained to the difference
in the EOC-2 and Hipparcos catalogues (Damljanovi´c and Pejovi´c, Serb. Astron. J. 173, 2006). The main
result of the thesis is the catalogue of proper motions in declination of 2347 Hipparcos stars. It is presented
in Table 27. |
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