用光电等高仪Ⅰ型的观测建立连续的赤纬系统──临潼－伊尔库茨克等高仪国际合作观测的意义

THE ESTABLISHMENT OF A CONTINOUS DECLINATION SYSTEM WITH PHOTOELECTRIC ASTROLABE MARK Ⅰ──THE INTERNATIONAL COOPERATION BETWEEN CSAO AND VS NIIFTRI

本文提出了利用陕西天文台光电等高仪Ｉ型和伊尔库茨克合作观测的建议。由于该仪器将配备Ｚ＝４５°的角镜，放在＝５２°的纬度上，就可以消除等高仪测定赤纬的盲区，从而可对建立基本参考系及将来维持伊巴谷星表系统做出重要贡献。

Owing to the unique characteristics of Chinese photoelectric astrolabes,the observation data obtained with the instruments played an important role in the improvement of FK4 Catalogue system.The recalculated observation data of Photoelectric Astrolabe Mark I(PHA I) show that the systematic errors of △αδ and △δδ may still remain in FK5 Catalogue,but are smaller than those in FK4 Catalogue.In order to make more contribution to the improvement of fundamental reference system with PHA I,an international cooperation project between CSAO (Shaanxi Astronomical Observatory,Academia Sinica) and VS NIIFTRI (East Siberian Research institute for Physics Technical and Engineering Measurement,Russia) by moving PHA I to VS NIIFTRI has been proposed.According to the principle of equal altitude method,there must be a blind declination zone for determining the errors of declination with the data observed by an astrolabe if Z+<90° as almost all the existing astrolabes in the world have,except for the PHA III of Beijing Observatory which is now under the testing observation,(where Z,the zenith distance of the almucantar and ,the latitude of the site).PHA I will reach the limited magnitude of 9m-10m by means of photon counting detectors.And it will be equipped with a new prism to make Z=45°,so Z+=97°.3 will be realized at VS NIIFTRI.There will be no longer the blind declination zone and a large declination range (over 70°) mag be covered for determining △δ with high precision.Fig.1 and Table 1 give two examples of blind zone and their estimated precisions (rather low near the blind zones),and the estimated precisions of the proposal.In part 3,three different methods used to determine the constants K and D in formula (1) are presented and the precisions of determining K an D are discussed too.It is clear that K and D will be satisfactorily obtained with two of them.It is indicaled in the forth part of this paper that observations for all the stars are made with equal precision of σz theoretically,which is usually misunderstood as the faster of transit,the higher of the precision.In fact,the precision would even be higher for slower transit stars bacause the atmospheric effects could be reduced by the longer sampling time.In addition,the ways to further improve the precision of the observations with PHA I are described.Hopefully the cooperation will make a greater contribution to the improvement of the fundamental reference system.