In 1880 Yale ordered a 6-inch heliometer from Repsold of Hamburg which was delivered on time for observations of the transit of Venus in 1882. Stellar astrometry, however, was not begun until W. L. Elkin came to Yale in 1884. Trained at Strassburg his Ph.D. dissertation dealt with the parallax of α Centauri (Elkin 1880). He then gained practical experience with Sir David Gill at the Cape. Elkin was the ideal man for the Yale heliometer and to secure his appointment H. A. Newton (1884) solicited subscriptions of $100 per year for three years from ten officers and friends of the observatory.

Details of the organization of the 1887 astrophotographic congress have been traced in Paris Observatory archives. The following points have been especially examined: invitations, practical organization, budget, decorations and reports edition. Amiral Mouchez personality becomes apparent after the factual knowledge.

At the International Congress of Astronomers that met in Paris, in 1887, to plan the mapping of the sky by photography, British observatories undertook the photography of approximately quarter the sky. This paper describes the contribution to the Astrographic Programme of these observatories and of other British establishments that subsequently offered to participate in the project.

Thomas and Howard Grubb, father and son, made telescopes in Dublin from c.1830 to 1925. The elder Grubb's first telescopes of some size were the 1835 equatorial mounting of a 34-cm Cauchoix objective for E. J. Cooper of Markree Castle, Co. Sligo, Ireland, and a 15-inch reflector for Armagh Observatory (1840), which employed a centrifugal governor and the first mirror-cell with rocking support pads. The firm continued in Newcastle-upon-Tyne in England as Sir Howard Grubb, Parsons and Co.

In this centenary commemoration of the Paris Astrographic Congress it is appropriate that we should recall the very significant role played by David Gill, Her Majesty's Astronomer at the Cape of Good Hope, in pioneering the application of photography to mapping the sky, and in the planning of the great Carte du Ciel project itself.

The various steps for the derivation of a fundamental catalogue are described and a report on the present status of the work on the FK5 is given. The observational material for the determination of the FK5 system is described and the systematic corrections to the FK4 are discussed.

Various techniques have been used to evaluate and describe coordinate system irregularities. The basic techniques have developed from simple differences to differences in coordinate “bins” to full spherical and cylindrical harmonic treatments. We are undertaking a 15-year program of minor planet observation with the express purpose of finding basic parameters of the adopted fundamental system with respect to a dynamical reference frame. The program is expected to provide a few hundred observations per year of 34 minor planets selected for their distribution of physical and orbital characteristics. The ability of the program to contribute to our knowledge of the rotation of the fundamental system and systematic irregularities within the system will depend on the accuracies of the observations and the distribution of the observations over the orbits and over the celestial sphere. We are considering the use of splines as a method of evaluating systematic corrections to the extant fundamental system. The initial development of the formalism and prospects for evaluation are presented.

The Eichhorn method of simultaneously estimating both target parameters and model parameters is applied to the compilation of a complete star catalogue. The input material of the Northern International Reference Stars (NIRS) is used and the resulting catalogue is compared to the NIRS catalogue compiled by Corbin (1977) using traditional techniques. By simultaneously using all available constraints on all available data, it is shown that the new estimates of the star parameters have smaller formal errors than estimates derived from the same material but using conventional procedures. Both versions of the NIRS are used to predict the star positions of the later observed Perth 70: A Catalogue of Positions of 24900 Stars and these predicted positions are compared to the actual observed positions. It is found that a simultaneous reduction results in a slight but significant improvement in the declination system of the NIRS.

An almost fully automatic scheme has been developed which produces final positions in the system determined by the reference catalogue, cross identifications, and approximate magnitudes in a standard system. A plate-overlap method is used which permits inclusion of higher order terms either plate by plate or common to a subset of plates. Magnitude dependent errors are also included. The system has already been applied to more than 500 plates, most of them of the Paris zone, with smaller sets of the Oxford, Potsdam, and Helsingfors zones. The Paris zone yields consistent higher order and magnitude terms over the entire set analyzed so far.

The principles of focal-plane astrometry are described, as well as the development of the overlapping-plate method. In particular, the advantages and pitfalls of this method are discussed. An extensive bibliography is appended.

A preliminary classical plate adjustment (CPA) of the Cape zone (−40° ⩾δ⩾ −52°) of the Second Cape Photographic Catalogue (CPC2) has already been published (Nicholson et al 1984). A status report of the whole CPC2 project which provides a fourfold overlap of the entire southern hemisphere on 5820 plates with two exposures each, has been given elsewhere at this symposium (de Vegt et al 1987).

The objective of the present study is to clarify the tests, checks and clues one may employ to determine whether a feature on a one century old plate is probably identical to a feature on a recent Schmidt plate. A test region of 40′ × 40′ around star HD 42088 was selected in order to detect a variability in nebulosities around Gem OB 1 stars.

Starting with the Astrographic Catalogue as the first example of an all sky coordinated international astrometric project, a considerable number of large photographic catalog projects has been accomplished in the last decades on both hemispheres. The accuracy properties and possible improvements of some catalogs by remeasurement, application of modern reduction techniques and the use of improved reference star catalogs will be discussed.

The optimal use of modern photographic technology and instrumentation for the construction of new global catalogs, capable of positional accuracies on the level of a few 0.01 arcsec, will be outlined with special view to an extension to fainter limiting magnitudes.

An astronomical overview of the Guide Star Catalog, together with its history, the properties of its current implementation, and the prospects for enhancement are presented.

The algorithms used in photometric and astrometric calibration of the Guide Star Catalog, as well as the analyses of the related errors are discussed. The precision requirements of for relative positions and of for photometry are generally fulfilled.

The current structure and content of the Guide Star Catalog (GSC), as well as future enhancements in this area are described. An overview of the forthcoming publications is given, both with regard to scientific papers and electronic media.

The various characteristics of the HIPPARCOS Input Catalogue are described:

1. – How to select 110 000 stars for HIPPARCOS observation from the 210 000 proposed stars, taking into account the following sometimes conflicting requirements : satisfy a maximum of scientific programmes and respect the observational constraints inherent in the HIPPARCOS satellite operation ?

2. – What are the present results regarding the principal astrometric programmes ?

3. – How to process the specific problems which are raised by the HIPPARCOS observation of double and multiple stars and of stars in dense areas ?

4. – Which compilations and observations have been undertaken and are in progress within the frame of the Input Catalogue preparation ? What will be the quality of the final data ?

Finally, the contents of the catalogues and annexes that will be published are briefly presented.

Hipparcos will measure positions, proper motions and parallaxes for about 110 000 stars brighter than B = 13, with an expected mean error of 2.10−3 arcsec in positions and parallaxes and 2.10−3 arcsec/year in proper motions. The contents of the first provisional catalogue with respect to astrophysical problems is described, and the star distribution versus spectral type, magnitude and distance is given. All types of stars are well represented (spectral types, various evolutionary stages, giants, white dwarfs, …). Precise parallaxes for 29 000 stars closer than 100 pc will provide a new base for luminosity calibration, and will allow accurate stellar masses to be determined from double stars with known orbits. Precise proper motions, in conjunction with the improved distances, will substantially improve our knowledge of galactic structure. All types of stars used for the cosmic distance scale calibration are well represented: Cepheids, RR Lyrae, supergiants, open cluster stars.

The real-time attitude of the HIPPARCOS satellite (see Turon, this symposium) is monitored by a star mapper viewing a 40 arcmin. Wide band of the sky, ahead of the main field of view, through a system of four vertical and four inclined slits (fig. 1). The resulting on-board precision will be 1 arcsec. rms and on-ground attitude reconstitution will later improve this value to 0.1 arcsec. rms.

The TYCHO project (approved by ESA in 1981) consisted in introducing dichroic beam splitters and a pair of redundant photomultipliers (with a bandpass close to Johnson B and V) into the science payload. This configuration will give a complete survey of the sky down to 11th magnitude in B, during the two and a half years of the mission. The data reduction is prepared by a scientific consortium (TDAC) which will be described in more details in section 4. The work related to the TYCHO Input Catalogue is described in section 2. An overview of the data reduction process is given as section 3, and aspects of the TYCHO outputs are discussed in section 5.

A new edition of the General Catalogue of Trigonometric Stellar Parallaxes is being prepared at the Yale University Observatory. The Catalogue will include all published photographic parallaxes, a reference to the source of the published parallax, UBV photoelectric photometry, MK spectral types, cross identifications with other catalogues, data on the binary nature of the stars and auxiliary information to aid in determining the reliability of the data. An analysis of the parallaxes corrected to absolute has been made to study the accidental and systematic errors of the parallaxes. The new edition will be available in both printed and magnetic tape versions.