Speckle interferometry, which is characterised by diffraction limited resolution and enhanced accuracy, offers a wide range of possibilities for astrometry. Speckle applications are limited by the constraint of isoplanicity with the result that only differential rather than absolute astrometry can be carried out with the technique. Nevertheless, potentially important applications exist in solar system and stellar astrometry, but speckle interferometry has so far made significant contributions only in binary star astrometry.

The CCD speckle camera now in use at Georgia State University has brought about considerable improvement in limiting magnitude and photometric accuracy over the old photographic system, but has also necessitated considerable changes in data storage and reduction. These new data handling techniques are outlined, with a few words about overall accuracy and a brief description of new equipment which should further improve our speckle program at GSU.

Infrared speckle interferometry combines the full resolving power of large telescopes with high photometric sensitivity over the wavelength range 2.2 to 12 microns. Despite improved atmospheric seeing at these wavelengths, seeing fluctuations limit measurement precision. Astrometric companions have been detected with angular separations ≥0.1 arcsec and magnitude differences ≤3.7 mag. Results illustrate seeing limitations and show how the usual position angle ambiguity can be overcome. These measurements yield masses and absolute magnitudes for calibrating the lower main sequence. In some cases, orbital motion is detected. A method of “shift-and-add” enables detection of substellar (0.04 to 0.08 M⊙) companions. Future improvements involving detector arrays and seeing monitors are discussed.

A small astrometric optical interferometer, Mini-POINTS, which would fit fully assembled in about one-third of the Shuttle bay, could measure the angle between stars about 90° apart. For 10th magnitude stars, an observation time of about 20 minutes would yield a measurement uncertainty of 5 microarcseconds. When compared to an astrometric telescope of comparable size which observes the same target for the same period of time, such an interferometer would achieve a greater accuracy by two to three orders of magnitude. Five design criteria lead to an instrument that achieves high precision by employing photon statistics for fringe splitting and achieves high accuracy by means of continuous internal metrology with laser interferometers. The high throughput of Mini-POINTS permits a mission design that addresses a wide variety of scientific questions.

A 3-meter two telescope stellar interferometer has been used to observe fringes for the past year in order to study the feasibility of using long baseline interferometers for astrometry. We have demonstrated that two color fringe measurements are capable of significantly reducing the astrometric error due to atmospheric turbulence. Currently, we are investigating the thermal and mechanical sources of error in the instrument. The results of our study will be incorporated into the design of the 20 meter astrometric interferometer which will be built in the next 1–2 years. The key to the 20-meter interferometer is the laser system which we expect to monitor all the mechanical and thermal imperfections relevant to astrometry at the 10−3 to 10−4 arc sec level. A slight modification of this system could be used in a space based interferometer for 1 to 10 microarcsecond astrometry of faint objects.

The 30-inch Thaw Refractor of the University of Pittsburgh's Allegheny Observatory has been completely rebuilt. Changes include a new objective lens, a new detector system, and computer control and data acquisition. With an observational accuracy exceeding one-thousandth of an arc second, the new system will greatly expand the domain of astrometric research.

Consider the possible astrometric use of the following concept: If the image of a field of stars is moved past a high-speed detector array at a precisely known velocity, relative positions can be determined by measuring time intervals. Attractive features of this approach are: times can be measured very accurately with photoelectric detectors; a relatively large area of the sky may be swept for reference stars; the images are measured essentially on-axis; and seeing effects can be partially frozen out. The only available detector with spatial and temporal resolution and stability adequate for this technique is the MAMA. A rudimentary observational test with this detector has yielded promising results. Further observations are planned to determine whether milliarcsecond accuracy can be obtained.

A SIT-Vidicon camera has been used for astrometric and photometric observations: phenomena of the Galilean Satellites, occultations of stars by asteroids and comets, closest approaches of fast moving objects. This paper tries to give a preliminary evaluation of the efficiency of these observations.

At the Shaanxi Observatory, regular observations with the prototype of the photoelectric astrolabe PAI have been carried out since 1973. Three photoelectric astrolabes of type Mark II (PAII) were mounted at the Shanghai, Beijing and Yunnan Observatories in 1974, 1976 and 1978, respectively. Details of the instruments and the results of the observation were published previously. (Photoelectric Astrolabe Developing Group 1973 and 1975, Second Group, First Divsion Shaanxi Observatory 1974, Astrolabe Data Analysis Group, First Division, Shaanxi Observatory 1975, Wang, L-j 1979, Astrolabe Group, First Division, Shanghai Observatory 1976, Wang, L-z and Luo 1979, Lu and Luo 1979). Time and latitude determinations by these sets of photoelectric astrolabes form a part in the international cooperation of BIH, IPMS as well as in the short campaign of project MERIT.

The meridian circle installed at the Tokyo Astronomical Observatory in 1982/83 is equipped with a photoelectric Double Slit Micrometer which is one of the basic prerequisites for fully automatic observation. A slit plate is located in the image field of the telescope. It oscillates parallel to right ascension while being guided at the mean traveling speed of the star.

The paper describes the procedure by which the moment of the star passage through the instrument's meridian and declination is determined. Furthermore, the autocollimation devices are described which are an essential prerequisite for the determination and periodical checking of the instrumental errors.

Also, the measuring devices for the passage of the sun and the moon are dealt with briefly.

To obtain a quite impersonal astrolabe, a new instrument has been built. The first UTo-UTC results show very good agreement with the BIH scale.

The Danjon Astrolabe at the Naval Observatory has been traditionally used to determine Universal Time and improve the systematic accuracy of star positions. During the past year, it has been used to determine latitude and longitude at remotely scattered sites for geodetic purposes. Operating this instrument away from the Observatory necessitated a mobile support and timing system rugged enough to operate dependably in ever changing, and sometimes harsh, environmental conditions.

This paper describes the performance of the astrolabe timing and data acquisition system, gives engineering design considerations, and describes the equipment and instrumentation.

The paper reports on the new semiautomatical meridian circle of the Pulkovo observatory. It is equipped with a scanning photoelectric micrometer and a photoelectric circle reading system. The standard errors of a single registration of a star are 0s.016 and 0″.35 in RA and declination, respectively. The limiting magnitude is 10.5m. The instrument can be used for IRS differential observations.

Some aspects of the design for a Glass Meridian Circle with 24 cm aperture are presented and discussed. Tangential ventilation will be used to minimize tube refraction. The air for the ventilation will be filtered and it will provide a clean atmosphere around all optical and critical mechanical components, thus improving reliability. The base frame and piers are particularly stable thanks to a sharp separation between parts with short and long thermal time constants. The instrument is compact and portable and it requires only a small dome.

This paper describes a conceptual design for an automatic transit circle with Ritchey-Chretien Cassegrain type optics of 40 cm aperture. The instrument takes reversal observation both in the meridian and in the prime vertical. Methods of adopting active optics to achieve a stable boresight of the reflecting telescope and of automatically reversing and leveling the instrument are presented. The instrument can also be used in a theodolite mode.

The space based determination of astronomical data will have significant advantages over the ground based ones. However, in the mean time the requirements for traditional astrometry technique do not decrease, but, on the contrary, increase, especially in view of the existing plans for large programs of ground based determinations of absolute and differential positions of stars and solar system bodies.

The conventionel reversible meridian circle of Copenhagen University, has over the last years been fully automated, and equipped with a new photoelectrical transit micrometer and a revised photoelectric circle recording system. Setting, observation and data recording is completely controlled by two minicomputers, therefore the presence of an observer is needed only for emergency situations, and for the reduction procedure. The telescope has been succesfully tested over a two year period in Brorfelde, resulting in two published catalogues with mean errors similar to those previously obtained with the photographic micrometer. The magnitudes were also measured and the limiting magnitude in Brorfelde was mv = 12.

In the autumn of 1983 the telescope was moved to the Canarian island La Palma, where it is currently being installed.

The Bordeaux automatic meridian circle has been used for routine differential observations for three years. Current programs concern NPZT stars, faint nearby stars from the Gliese catalogue, Mars, Uranus, Neptune, Jupiter and Saturn satellites, and minor planets. From 1984 on, 5000 faint stars from the HIPPARCOS Input Catalogue will be observed.

Anderlucci et al. (1983) describe a multislit photoelectric micrometer attached to the transit instrument of the Observatory of Torino and report some preliminary results.

Definitions of Instantaneous Instrumental Coordinates and Local Horizontal Coordinates of the photoelectric meridian circle of Tokyo Astronomical Observatory are given, and a method to determine the positions of stars by using a scanning double slits micrometer are presented. It is found that stars up to 12.2 mag are observable by making a composite photon intensity. Discussions on the application of observations of faint objects by meridian circles are presented.