Contributions made by Vassily Yakovlevich Struve and his son Otto Vassilyevich to the eventual establishment of an inertial frame of reference on the sky are discussed under five heads: (i) the foundation of Pulkovo Observatory, (ii) instrumentation, (iii) Vassily Yakovlevich's determination of the constant of aberration, (iv) Otto Vassilyevich's determination of the coefficient of precession and (v) international cooperation.

The most significant basis of the reputation of a scientific organization is the accuracy and influence of its work. From a comparison of values of certain astronomical constants and stellar parallaxes obtained at Pulkovo and elsewhere, the extremely high weight given to the Pulkovo values (e.g. by Newcomb) is further justified in retrospect given the small deviations between Pulkovo values and the “modern” values accepted a century later.

The longest geodetic arc ever mesured by classical goedesy is long of 25° from the Baltic to the Black Sea through the Dorprat meridian. This arc is based upon measurements made, from 1816 to 1855, by a russian general, a norvegian, a Swedish and F.G.W. Struve, the founder of the Pulkovo Observatory; its lenght is 2° more than the arc Delisle, then at the Petersburg Observatory, intended to determine along the meridian of this observatory in the year 1737. Russia, at that time, became part of the european triangulation, a prelude to circumterrestrial modern campaigns.

The patronage of national governments has played an important role in the history of astronomy, classically in the form of National Observatories. In this paper we 1) argue that the last three centuries have seen what we may call a “national observatory movement,” in that national governments during this period increasingly supported astronomical observatories, and in that such institutions share certain common properties of origin, purpose and evolution; 2) demonstrate the important role that Pulkovo Observatory has played in this movement; and 3) compare certain aspects of the Pulkovo Observatory and the United States Naval Observatory as exemplars of this species founded within a decade of each other under very different political conditions.

Standard values of astronomical and geodetic constants were adopted in the late nineteenth century for use in the determination of terrestrial and celestial coordinates, and their values were changed subsequently as better values became known. The great improvements in the precision of observation during the past decade has made it necessary to develop reference systems that also include the models and procedures that are used for the analysis of observations by particular techniques. The accurate detemination of the connections between the corresponding reference frames and the adoption of unified standards are major tasks for the future.

The IAU Working Group on Reference Systems (WG) was founded by a Commission Resolution passed at the XXth General Assembly in Baltimore in 1988. Since most, if not all, participants in this meeting are familiar with that resolution, it will not be discussed here. Background material may be found, for example, in Highlights of Astronomy, XX General Assembly (1988, Ed. D. McNally). Particular attention is called to the reports by B. Morando, R. Duncombe and J.A. Hughes (pp. 482-500) which were given as part of the Joint Commission Meeting, Towards Milliarcsecond Accuracy, chaired by P.K. Seidelmann. This short presentation will provide a description of the current state of affairs of the WG, which is chaired by the speaker.

In 1978, Guinot proposed that, for studies of Earth rotation, the zero point of the apparent “right ascension” coordinate on the true equator should be so chosen that the rate of change of its hour angle is exactly proportional to the inertial rate of rotation of the Earth. It has been subsequently suggested that this concept of the “non-rotating origin” supersede the equinox quite generally as the origin of celestial coordinates. Since this proposal was first put forward, there has been much discussion, and some criticism, from Aoki and his colleagues, both published and in private correspondence. Some of the arguments for and against Guinot's proposal are discussed, as a contribution to the wider debate on reference systems now being carried out under the auspices of the IAU.

The observation of visual double stars at Pulkovo is a traditional work of Pulkovo astronomers started by W. Struve in 1830 at Dorpat (now Tartu). After the Second World War and restoration of the observatory in 1960, the observations of double stars have been carried out with help of 26-inch Zeiss refractor using the photographic technique. We observe the visual binaries which satisfy the conditions of highest accuracy of astrometric reduction: d > 3′, m < 12.0, dm < 1.0, δ>20°.

The Pulkovo program of determination of proper motions with respect to galaxies approaches completion. It consists of 157 fields from +90° to −4° of declination. The proper motions and reductions with use of galaxies were derived for all areas. The errors of reductions are equal to ± 0.″006. In addition the statistical reductions Rx, Ry were computed for the control and for the zones of avoidance. The following formulae were used: where is the secular parallax according to Binnendijk [1]; P and P′ are parallactic factors; Q and Q′ are members dependent on the galactic rotation.

The most widely spread method of determination of star declinations is Bessel's method. Alhough it gives good agreement between star declinations obtained from observations of stars in upper and lower culminations, it leads to great systematic errors if the system of the instrument has an error of the type such as flexure or errors of divided circle. Besides, in the determination of correction of latitude (Δφ) and refraction (Δμ) considerable correlation between them exists.

The Photographic Vertical Circle (PVC) was constructed in Pulkovo shops in 1962 according to idea of M. Zverev for absolute determinations of declinations of stars. Observations were made at the observatory Serro-Calan in Chile by Chilean and Soviet astronomers in 1964-1966. The PVC is an experimental instrument: it is the first reflector and the first photographic instrument for absolute observations. It has two circles and each circle has four photographic microscopes.

The programme of observations of 10 bright minor planets for 1991-2000 is proposed. One of the main aims of the programme is the determination of the orientation parameters and the systematic errors of star catalogues.

For astronomical, geodetical and geodynamical investigations as well as for practical applications the inertial coordinate system is widely used which is based on the Fundamental Star Catalogue FK5 together with local coordinate systems in observation stations on the Earth's surface which are intrinsically connected with the geometry of the gravitation field.

The satellites of Mars, the Galilean satellites of Jupiter and the first eight satellites of Saturn have been observed with the 26-inch refractor, the normal astrograph at Pulkovo and with the luni-planet telescope at the Ordubad station of the Pulkovo observatory since 1972.