Driven by her personal interest, Baroness Matt erected a private observatory in Vienna, bought and ordered precise instruments and carried out astrometric and geodetic observations at several places in Austria and in western Bohemia. Unfortunately her activities were hampered by the Napoleonic wars and were cut short by her early death.

In his journals which were devoted mainly to astronomy, Franz Xaver von Zach also presented geographical and geodetic information about Australia. Initially these accounts were in German, but towards the end of his life he wrote them in French for a more general audience.

We compare the W velocity dispersions of Brosche, Schwan & Schwarz (2001) with more recent results. The increase with the distance | z | from the galactic plane is confirmed, although perhaps with reduced amplitude. This could be interpreted either as one homogenous population or as a superposition of (at least) two populations with two constant dispersions and two scale heights. For each of the possibilities we propose a simple model. Combined with two observational variants for the velocity variation, we obtain surface densities up to | z | = 250 pc ranging from 5 to 44 M ⊙ pc –2 . Thus the case for considerable dark matter in the neighbourhood of the galactic plane is not supported

The last line of the abstract should read “about μ = 10–5c 2/G. This corresponds to 1.2 · 1039 Newton”. The main text remains unchanged. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We start from our extended scenario for the formation of astronomical objects from fragmenting macroscopic superstrings, and we combine it with our view of an “orderly” fragmentation applied to the formation of black holes (Brosche, Lentes & Tassie 2003), now to the whole objects: the radial order of the matter should be preserved. Then we have to adapt the value of the superstring tension derived from the observed ratios of κ = (angular momentum)/(mass squared). If we calculate potential energies on the basis of a fragmentation until baryonic elementary particles, it turns out that the changed string tension explains as well the mechanical state of observed astronomical objects (without large energy loss on the way from the parent string parts) as also the fraction of bound to unbound matter (about 1:10). The implied superstring tension is about μ = (1/3000) c 2/G . This corresponds to a string tension of 4 × 1040 Newton. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We augment our scenario for the formation of astronomical objects from macroscopic superstrings by the assumption that the central matter keeps its identity in the fragmentation. From the condition that the angular momentum per mass squared of this matter should be less than the Kerr limit G/c, we obtain upper limits for the ratio of the mass of central black holes M(BH) to the mass M of the host object. This limit is M(BH)/M ≈ 0.001, and, expressed in observed quantities, approximately M(BH)/M ≈ σ2/(v · c) where σ is the r.m.s. velocity, v the rotational velocity and c the velocity of light. The valuesM(BH) agree with the observed behaviour both in order of magnitude and in the variation with velocity dispersion. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We have investigated the motions of all K0-5 stars which have a proper motion in the Hipparcos catalogue and a known luminosity class III (due to the incompleteness of the ongoing classification, the distribution of these stars at the celestial sphere is rather uneven). We have used the apparent magnitudes and colours together with adopted means and dispersions of the absolute values in order to estimate distances. The fulfilment of two one-sided conditions has been ensured: the stars should only be reddened and their photometric parallaxes should be consistent with the trigonometric ones; this is practically a one-sided condition, if, as usual, the trigonometric parallax is near zero (every condition to be demanded within s dispersions). Our final total sample contains 8349 stars. We did not demand the knowledge of radial velocities or metallicities, nor did we use them in the rather small fraction of our stars which they were known for. The estimated photometric distances have a logarithmic mean of 280 pc and an error of typically 25%. The proper motions were represented by a kind of ‘adaptive’ model, using a three dimensional expansion in a series of orthogonal functions of galactic latitude, longitude and of the logarithm of the distance. Our programme searches automatically for significant functions. Usually, we have selected those which could arise by chance with a 5% probability only or less than 5% (in some cases we additionally have treated the data with a corresponding limit of 1%). Most of the found significant functions belong to exact or approximate equivalents of known standard motions, especially the average ensemble motion and the two first order parameters of galactic rotation. The data were treated first for each spectral subclass separately and then - since the differences were not pronounced - as a united sample. For the united sample, the ensemble motion with respect to the sun is (U0, V0, W0) = (—9.0 ± 0.5, —21.0 ± 0.5, —7.7 ± 0.4) km/s and with respect to the local standard of rest (U, V, W)LSR = (+1, —16, —1) km/s As galactic rotation parameters we obtain Q = —1.81 ± 0.51 mas/yr, P = +2.92 ± 0.32 mas/yr (the first being corrected for asymmetric drift with the aim to represent the circular velocity). Beyond these standard motions, three non-standard functions appear. One of those has a 4 s coefficient and corresponds to a distance dependent galactic shear parameter C. If we were to demand that this term vanishes, Q would change towards —2.60 mas/yr - in agreement with the value from Hipparcos Cepheids. The residuals against the systematic motions are used to obtain the 3 axes of a velocity ellipsoid (assumed to be aligned to the galactic axes) σ(U) = 37.5 ± 0.3 km/s, σ(V) = 26.9 ± 0.4 km/s, σ(W) = 20.1 ± 0.7 km/s. The two quantities V0 and σ(U) mutually fulfill the asymmetric drift relation. From the total dispersion an age of the order 4 · 109 years can be obtained. These figures agree with those of nearby old giants, but they now refer to a much larger volume and number of stars. All dispersions depend on the distance z perpendicular to the galactic plane. Most distinctly, the dispersion perpendicular to the galactic plane cannot be described by one isothermal component. σ(W) increases with |z|; the distribution of the W-velocities near the galactic plane is non-Gaussian in the sense that the central peak is more populated. Thus at least 3 components would be required if a description with isothermal components were wanted.

The main aim of this paper is an extension of the heuristic concept of the tidal radii of globular clusters to the case of very non-circular orbits, i.e. with large differences between the peri- and apogalactic distances. We had found earlier that perigalactic tidal radii do clearly not represent the observed limiting photometric radii. For 16 globular clusters with orbits based on absolute proper motions we derived instantaneous tidal radii along the orbit. We computed four kind of averages of the instantaneous values. The comparison between average tidal radii and observed limiting radii relies on the ratios between the two, since the equations for the theoretical values may need the inclusion of an additional constant factor. In case that the said ratios do not depend on the shape of the orbits, we consider the underlying method of averaging as satisfying. In a quantitative approximation, this non-dependence can be assumed for all methods within 3σ-limits; but one method stands out in that it fulfils it within 1σ. This method or way consists in forming the reciprocal squares of the instantaneous tidal radii and their mean along the orbit.

The errors of the lunar ephemeris of Regiomontanus are a function mainly of lunar age. This is because the "variation" in the modern theory has no counterpart in ptolemaic theory. In addition to this sinusoidal error constituent (with zero point at syzygies and an amplitude ±0°.66 at the first and last quarters), there is a constant error due to longitude inconsistencies and a random part ±0°.5 from various sources.

We present an investigation of the differences between quasi-instantaneous stellar proper motions from the Hipparcos catalogue and long-term proper motions determined by combining Hipparcos and the Astrographic Catalogue. Our study is based on a sample of about 12000 stars of visual magnitude from 7 to 10 in two declination zones on the northern and equatorial sky. The distribution of the proper-motion differences shows an excess of large deviations. This is caused by the influence of orbital motion of unresolved binary systems. The proper-motion deviations provide statistical evidence for 360 astrometric binaries in the investigated zones, corresponding to about 2400 such binaries in the entire Hipparcos catalogue, in addition to those already known. In order to check whether the observed deviations are compatible with standard assumptions on the basic parameters of binary stars, we model the impact of orbital motion on the observed proper motions in a Monte Carlo simulation. We show that the simulation yields an acceptable approximation of the observations, if a binary frequency between 70% and 100% is assumed, i.e.if most of the stars in the sample are assumed to have a companion. Thus Hipparcos astrometric binaries confirm that the frequency of non-single stars among field stars is very high. We also investigate the influence of the mass function for the secondary component on the result of the simulation. A constant mass function and mass functions with moderate increase towards low masses lead to results, which are compatible with the observed proper-motion effects. A high preponderance of very-low-mass or substellar companions as produced, for example, by a M—1 power law is not in agreement with the frequency of proper-motion deviations in our sample of stars.

“Salvaging an astrometric treasure” is an european effort to retrieve the astrometric and photometric information contained in the early Carte du Ciel plates. Five institutes from three european countries are involved. The project was supported by the European Community.

A new procedure for the reduction of "Carte du Ciel” plates is presented. A typical "Carte du Ciel” plate corresponding to the Bordeaux zone has been taken as an example. It shows triple exposures for each object and the modeling of the data has been performed by means of a non-linear least squares fitting of the sum of three bivariate Gaussian distributions. A number of solutions for the problems present in this kind of plates (optical aberrations, adjacency photographic effects, presence of grid lines, emulsion saturation) have been investigated. An internal accuracy of in x and y was obtained for the position of each of the individual exposures. The external reduction to a catalogue led to results with an accuracy of in x and in y for the mean position of the three exposures. A photometric calibration has also been performed and magnitudes were determined with an accuracy of .

The aberration of starlight seems to be one of the simplest phenomena of astronomical observation. However, the story of misunderstandings is long and lasts till now. It is nearly forgotten that the problem of stellar aberration was the cornerstone of the development and the acceptance of relativity. In addition, there seems to be no essentially final point in the discussion of its interpretation, the discussion seems to merely be given up. Of course, with the correct relativistic formulas, there is no need of interpretation any more. The price of this consists in the many incorrect descriptions and interpretations that arise if a textbook tries to explain in words the mere formulas. We try to review the problems discussed in the last three centuries and to give them a final, i.e. geometrical form. We are convinced that this teaches a lot about the geometry of the space-time union.

With the Hamburg geostrophic ocean general circulation model, the temporal variation of the angular momentum of the oceans is studied. The input wind stresses consist of climatological winds plus the deviations of the actual winds 1981-1989. The motion part of the angular momenta of the two hemispheres resembles the (counter-phase) behaviour of the corresponding atmospheric angular momentum. The dominating matter part however shows no phase shift between the hemispheres. The sum of the angular momenta of the solid Earth and the atmosphere is deduced from observations; in principle it should be inversely correlated to the oceanic angular momentum. A first attempt to recognize the correlation between these empirical data and the theoretical values is described.