In the context of the future Hipparcos astrometric satellite which will give a high precision catalogue, the ground based astrometry will have new possibilities of research, particularly in the field of the stellar and the dynamical reference systems. The modern astrolabes should give, as new photoelectric meridian circles, an important contribution.

Since 1956, the Danjon astrolabe was used to determine the Earth rotation parameters. Very rapidly it was demonstrated (S. Débarbat, J. Kovalevsky, 1963) that this instrument was able to give very good planetary positions, relatively to the FK4. New studies shown, later, that it was also possible to observe the Sun (F. Laclare 1975, N. Leister 1979, F. Chollet 1981). The major contribution of the astrolabe was the observation of stellar catalogues (Billaud 1978) and now, the determination of the variations of the solar diameter.

In these conditions, it is now possible to use polyvalent astrolabes, able to give good positions of stars, planets and Sun. The Hipparcos catalogue, connected to the extragalactic reference system by VLBI, will constitute a very precise “interpolation system”. The main problem will be to save this high precision during a long time. Without other Hipparcos satellite or other method, this problem can be solved only by the ground based astrometric observations. At the same time, some other fields of research can be initiated if the astrometric observations are directly connected to Hipparcos catalogue, such as the local effects, the refraction, the motions of the vertical, which will improve in the future the ground based astrometric results.

Concerning the astrolabes, some studies are made in France to improve the instrument and the methods of reduction. At the same time, the astrolabe community has to use the same procedures of observation and reduction to be able to connect the results coming from several different stations.

Photography of the southern hemisphere for the Second Cape Photographic Catalogue (CPC2) was commenced in 1962 by R H Stoy, HM Astronomer at the Cape. During the following ten years nearly 6000 plates, each having two exposures and covering 4° × 4° with fourfold corner to centre overlap were obtained. All plates have been measured on the GALAXY measuring machine at the Royal Greenwich Observatory under the general direction of W Nicholson. A preliminary catalogue giving positions and magnitudes of more than 50 000 stars in the Cape Astrographic zone (−40° to −52°) has already been published (Nicholson et al. 1984), together with details of the programme. Measurement of the plates, initial identification of star images appearing on all overlapping plates, and photographic photometry have been carried out at RGO; the subseqent astrometric data reduction is being performed at Hamburg Observatory.

The Multichannel Astrometric Photometer (MAP) now in use in the Allegheny Observatory astrometric program is the detector chosen for the strawman design of the Astrometric Telescope Facility (ATF) proposed for the U.S. Space Station. Extrapolation of ground based performance to above atmosphere observing conditions indicates an approximate precision of 0.00001 arc seconds per annual normal point.

MAMA was designed to digitize a Schmidt photograph in 2 hours, and a Carte du Ciel plate in 30 minutes, with a positional accuracy of 1 micron. Comparison of recent photographs with Carte du Ciel plates can thus be performed on a large scale to determine proper motions of stars down to visual magnitude 14 over a time interval of about ninety years. The poster presents the main features of the system and illustrates some programmes undertaken in various domains.

This paper reports the first results of solar motion and galactic rotation studies which are being done at Lick Observatory, using the new data from the Lick Northern Proper Motion (NPM) Program. This study finds: (1) A = +11.31 ± 1.06 and B = −13.91 ± 0.92 km/s/kpc, consistent with a nearly flat galactic rotation curve with a local circular velocity near 200 km/s; (2) solar apex locations lying near the standard apex for low galactic latitudes, but trending strongly toward the direction of galactic rotation for high galactic latitudes; (3) RMS external error estimates for the Lick proper motions: for the absolute zero-point in a typical NPM field, and for the overall systematic zero-point error. A more detailed presentation of these results has been given by Hanson (1987). The NPM program is reviewed in another paper in this Symposium, and has been described in detail by Klemola, Jones, and Hanson (1987).

An almost inertial celestial reference frame based upon extragalactic sources is in the process of being established. This reference frame is to be global with a minimum density of one source per 100 square degrees. The source positions will be based upon radio observations and will allow optical reference frames to be related to this frame at the 0.03 arc second level.

The redevelopment of the Minnesota Automated Plate Scanner (APS) is complete and the system is being used as an astronomical visitor facility. The system consists of the original CDC-Luyten scanner with a new microprocessor-based motion control system, state of the art detection electronics, a PDP-11/60 data acquisition system with all relevant scanning parameters under software control, a Sun 3/110 computer for data reductions and a high speed link to the University of Minnesota Supercomputer Institute Cray 2 for reductions of very large projects. The redeveloped APS is among the fastest plate measuring machines in the world and features a variety of densitometric and isophotometric data acquisition modes. An ambitious project is being undertaken to scan all plates of the first epoch Palomar Sky Survey. Objects will be classified as stars, galaxies, plate flaws, etc., and accurate positions and magnitudes will be determined. This resulting catalog, as well as the raw data archive, will be made available to the astronomical community.

The Astrographic Catalogue is the major source of accurate first epoch coordinates of stars down to about 11 mag all over the sky. Therefore it could be the ideal tool for the determination of proper motions in this range of magnitudes - see also for example Fresneau (1985). There were mainly three reasons which prevented in the past a frequent use of this catalogue:

1. 1) Apart from the „french“ zones (Lacroute 1981) the AC is not available in machine readable form.

2. 2) Only measured plate coordinates x,y and plate constants mostly derived with the AGK1 as reference catalogue have been published.

3. 3) The lack of easy to use software for a new reduction.

NASA is planning an Astrometric Telescope Facility (ATF) for the U.S. Space Station. Space astrometric observations of unprecedented accuracy will yield many important results, including a planetary detection survey. The proposed facility is a dedicated astrometric telescope using the Multichannel Astrometric Photometer (Gatewood et al., 1987). To achieve the goal of sub-milliarcsecond accuracy requires innovative approaches to measuring technique and data analysis.

The programme for the determination of proper motions with reference to galaxies for 6000 stars on 17 fields near the main meridional section of the Galaxy is presented. For each field there are 2 or 3 first-epoch plates taken with the Tautenburg Schmidt-telescope before 1970. In preliminary investigations the mean error of an individual proper motion was found to be per century both for bright (8m–12m) and for faint (16m–18m) stars.

From a list of 275 confirmed or potential radio stars proposed to the Hipparcos input catalogue we selected about 80 objects which either lie outside the conventional astrometric catalogues or which are SAO-stars having declinations less than −17°. The positions of these stars were derived from measurements on POSS, SRC, and ESO(B) plates using reference stars from the SAO catalogue for the northern candidates, and from the Perth 70 catalogue for the southern candidates, respectively. The epochs of our positions fall in the middle of the fifties and seventies. For 52 stars other epochs were supplied by observations taken from literature. We determine proper motions from these positions which provide a base-line up to 35 years.

Intercontinental dual-frequency radio interferometric measurements were carried out during 1978 to 1985 between NASA's Deep Space Network stations in California, Spain, and Australia. Analysis of 6800 pairs of delay and delay rate observations made during 51 sessions produced a catalog of positions of 106 extragalactic radio sources, fairly uniformly distributed over the celestial sphere between −45° and +85° declination. Almost all of the resulting source positions have formal uncertainties between 0.5 and 3 milliarcseconds, with their distributions peaking somewhat below 1 mas. Root-mean-square uncertainties are 2.1 and 2.0 mas for RA and declination, respectively. Evidence is found for a long-term drift of the Earth's rotation axis in inertial space, relative to the 1984 IAU precession and nutation models. Tests for time variability of positions of 32 frequently observed sources place limits at the 1 mas/yr level. Comparisons with independently determined source catalogs of comparable quality show differences of positions of common sources that amount to a few mas, and may indicate the level of systematic errors in VLBI source position measurements.

The proper motions of the galactic globular clusters 47 Tuc and NGC 362 are currently being measured relative to the background of the Small Magellanic Cloud. This paper reports on the reduction routines developed so far for the simultaneous computation of several thousands of stellar proper motions. A preliminary result for NGC 362 is given.

Measures of 25 members of the Hyades and about 260 field stars have been made for parallax and proper motion in two ways, automatically using a PDS microdensitometer and manually using a conventional measuring machine. Reductions show the parallax errors from the former are about half those of the latter method.

The objective of this investigation is the determination of absolute parallaxes and proper motions with respect to faint galaxies for three fields at mid galactic latitudes and one field near the south galactic pole. The three mid galactic latitude fields were photographed on a IIIa-J + GG385 plate/filter combination by van Altena at the prime focus of the KPNO 4-meter in the mid 1970s, while the south polar region was photographed on a IIIa-F + RG610 plate/filter combination by van Altena and C.E. Lopez (Univ. of San Juan, Argentina) at the prime focus of the CTIO 4-meter; all plates were hypersensitized by baking and exposed to the sky limit. In this paper we report on the progress of an investigation of the mid galactic latitude field at R.A. = 7h 07m 31s and Dec. = +7o 19.7′ (1950) which contains the faint binary white dwarf LP543-32/33. Preliminary measurements of selected stars in this field were made some time ago and a parallax of the white dwarf binary were published by van Altena and Mora (1977). Those measurements showed that the plates were of very high astrometric quality and that it would be possible to obtain accurate parallaxes for very faint stars.

The main properties of the 1.56-m astrometric reflector of Shanghai Observatory are described. Some principles of selecting program stars are presented. The experimental program that has been performed with the Zô-sè 40-cm refractor since 1980 is outlined. Accuracies which are expected to be obtained for new program parallaxes are discussed.

The concept is developed for a scientific space mission to survey the entire sky and to image individual sources at frequencies between 1.5 and 26.3 MHz, a frequency range over which the Earth's ionosphere transmits poorly or not at all. The required technology already exists and there are many important scientific goals which can be attained with high sensitivity, high resolution space observations at the lowest frequencies available to astronomy from within the absorbing interstellar plasma of our own Galaxy.

We are investigating a complete sample of flat-spectrum extragalactic radio quasars drawn from the Parkes 2.7 GHz survey. The sample is being used to map the space distribution of radio quasars and to determine their luminosity function. Accurate positions are being measured for a selection of the brighter quasars in order to establish an extragalactic position reference frame in the Southern Hemisphere.

Nearly 20000 double stars have been detected from star positions listed in the Astrographic Catalogue. However, an examination of the various discoverer's efforts reveals that the past searches have been very incomplete. In fact, if the limits adopted by one discoverer were applied to the remainder of the catalogue, approximately 3·105 additional pairs would be found. Is such an endeavor justifiable scientifically?