A comparison of the SAO-Hipparcos reference frames

摘要: Abstract. The reference systems defined by the SAO and Hip-parcoscataloguesarecomparedusingvectorsphericalharmonicanalysis. differences between astrometric data in both cat-alogues have been grouped into different sets separateharmonic analysis performed on them. Fourier coefficientsyield estimates of systematic errors catalogue.Key words: astrometry – catalogs1. IntroductionThe Smithsonian Astrophysical Observatory Star Catalogue(SAO) has largely used as catalogue thereduction plates past. These con-tain relevant information comet asteroid positions andmotions.The International Celestial Reference System (ICRS) isnowadays conventional IAU System, material-ized primarily Frame(ICRF). optical realization ICRS is HipparcosStar Catalogue. recommended to perform all neces-sary ties frames nature serving variouspurposes, present realizations ICRS.We compared coordinate proper motion differencesbetween more than 100000 stars common Hippar-cos catalogues using vector spherical harmonic analysis. Theresults reveal distortions sphere through SAOstar positions, most important effects being declination,associated a large displacement field towards South pole.The coefficients series which represent differencesprovide tool transform reduced with SAOcatalogue ICRS.2. (ICRS)The celestial system Earth Rota-tion Service (IERS, Arias et al. 1995) was adopted since Jan-uary1998bytheInternationalAstronomicalUnion(IAU)astheconventional under name Inter-national (ICRS). follows