Marcin Sękowski - Monographic Series No 11
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The influence of choice of fundamental cataloque on calculated apparent places of stars
The paper has been inspired with changes of the concepts and definitions concerning celestial reference systems and frames approved and recommended by recent resolutions of the General Assembly of the International Astronomical Union. The paper is based in the doctor thesis defended by the author (Sekowski, 2005).
In two first sections there are presented: celestial reference systems based on fundamental catalogues of FK3, FK4, FK5, and contemporary, recommended by IAU International Celestial Reference System (ICRS), as well as its realizations (ICRF) based on the Hipparcos (HCRF) and FK6 catalogues (sec. 2). There is also described an apparent place as such, both in the context of catalogue systems and in ICRS including the subjects of: precession-nutation matrix, Besselian Numbers, Intermediate Reference Pole (IRP), and the concept of non-rotating origin (NRO) and Celestial Ephemeris Origin (CEO) (sec. 3). The respective computation algorithms are presented too.
Section 4 presents an extensive discussion of the results of computations made to compare the FK5 catalogue data with the contemporary Hipparcos and FK6 catalogue data.
Section 5, the most essential one, covers the subject of detailed analysis of the effect of fundamental catalogue data and the differences between the old and contemporary catalogue data on the values of calculated apparent places of stars. The effect of changes of precession-nutation model and definition of the celestial reference system is analysed too. The section contains also an analysis of time variability of the calculated apparent places and specifies the problems of interpolation and presentation of calculated data in a tabulated form used in the astronomic almanacs.
The last section 6 completes detailed results and conclusions drawn from the analyses and computations performed. These are: a conclusion of presence of large, reaching some hundreds of mas, systematic differences between the FK5 and Hipparcos catalogue data; showing the relative rotation of about 20 mas between FK5 and HCRF catalogue celestial reference frames; and pointing out the catalogue errors as the major source of the errors of calculated apparent places. Still, the switch from the FK5 to Hipparcos catalogue data and from FK5 to HCRF catalogue celestial reference frame gives an improvement in calculated apparent places accuracy by an order of magnitude.