Because of unforeseen difficulties, Dr Sinzi, President of the Commission, was not able to prepare this Report. It was then too late for asking the Directors of the almanac offices and the other Members of the Commission for informations. This Report is therefore based on the material just available, and it must be apologized for some lack from which it necessarily suffers. If possible, any omitted facts which appear to be serious, may be included in the Report for the following triennium.

The range of activities of Commission 5 has considerably broadened over the last decade, compared with its originally bibliographical emphasis. This fact is also reflected in the new name of this Commission as adopted at the Montreal conference. The increased production of astronomical data, the growing role of data centers in the organisation and retrieval of information, as well as the editorial and bibliographic processing of the large number of primary papers have indicated the need for new and more efficient coordinative guidelines. Several documents have been published and are under consideration, or are in preparation, for the agenda at the IAU General Assembly in 1982.

The Commission has been fortunate in being able to continue its work during the last triennium with a minimum of effort, and thanks for this should go largely to the Director of the Bureau, Dr B.G. Marsden, for his untiring dedication, as well as to the Smithsonian Astrophysical Observatory for its general support. If any question has arisen, it was where the line should be drawn between paid and unpaid contributions to the Circulars. This involves a somewhat delicate balance of interests between, on the one hand, the encouragement given to certain types of observations which have traditionally been published in the Circulars, (e.g. accurate positions of comets), and, on the other, the income on whi h the continued successful operation of the Bureau depends. The position will therefore have to be kept under review at all times. At present all evidence points to general satisfaction with current policy.

In the past three years progress of celestial mechanics research was as rapid as in the previous decade. In fact now new theories of planetary and lunar motions which have nearly the same accuracy as those of the most precise observations have become available after a decade effort and new thories of some of natural satellite motions have been developed by several authors. Many papers on artificial satellite motions from several aspects were still published and more precise expressions for relativistic effects were derived.

This report summarizes research on solar activity over an almost three-year period from January 1, 1979, till the end of June 1981. In preparing this report we respected the advice of the I.A.U. Executive Committee to cover the highlights of work carried out in the field of solar physics relevant to our Commission, and avoiding double work. Only a limited space was made available for our Commission. Given this restraint we tried to produce a comprehensive review. With great pleasure I appreciate the excellent cooperation of the members of our Executive Committee in the preparation of this report.

The report of Commission 12 presented here covers the parts of the field of solar physics other than those directly related to solar activities which, in our view, are the time-dependent phenomena inherent to solar active regions to be covered by Commission 10. From the sub-fields in the domain of Commission 12, the Organizing Committee selected six topics of special interest and invite six researchers to prepare reviews. Topics selected and reviewers are (1) Variations of Total Solar Irradiance ( Dr. R. C. Willson, Jet Propulsion Laboratory ), (2) Solar Global Oscillations ( Dr. E. Fossat, University of Nice ), (3) Magnetic Activity and Rotation in the Sun and Stars ( Dr. R. W. Noyes, Harvard University ), (4) Photospheric Magnetic Concentration and Related Problems ( Dr. H. C. Spruit, Max Planck Institut fur Astrophysik ), (5) Coronal Loop Structure and its Heating ( Dr. E. Priest , University of St. Andrews ), and (6) Coronal Transients ( Dr. E. Hildner, NASA Marshall Space Flight Center ). Of course it is not that there were no important contributions to the progress of sub-fields of solar physics other than those presented here. It was our consensus, however, that we should adopt this method since a complete coverage of works appearing across the entire field is no longer possible because of the rapid increase in the number of works in the expanding field of solar physics when severe page limitations exist for the IAU Reports.

The rapid expansion during the past few years of the spectral region accessible to astronomical observers, from gamma rays to the radio region, has resulted in a corresponding expansion of the need for a wide variety of atomic and molecular data. Included are needs for accurate wavelengths, atomic and molecular energy levels, and transition probabilities. The continually improving resolution that has been attainable has resulted in the requirement of improved insight into line broadening mechanisms of various types. This expansion has placed an increasing premium on data compilation and dissemination, so that available information can be made readily available to potential users. Among the numerous compilations that have appeared might be mentioned the important National Bureau of Standards Bibliography on Atomic Levels and Spectra, which is up-dated periodically via successive supplements, and the NBS compilation and bibliography by the Data Center on Atomic Transition Probabilities. Several compilations or bibliographies on collision cross-sections are now available, such as that published by the Information Center at JILA. In the field of molecular spectra there has appeared the very comprehensive “Constants of Diatomic Molecules” by Huber and Herzberg. Other useful compilations are referred to in the reports of the five Working Groups that appear below.

The illness which prevented Dr. N. Richter from presiding over Commission 15 sessions in Montreal proved fatal on November 26, 1980.

Books published since 1978 dealing with the subject matter of Commission 15 are: (1) Comets and The Origin of Life, ed. C. Ponnomperuma, 1981, D. Reidel pub. Co., Dordrecht, Holland (designated C. P. Colloq. in Report); (2) Comets, ed. L. Wilkening, Univ. Arizona Press, 1982 (designated Comets, 1982 in Report) contains invited reviews of Tucson, IAU Colloquium No 61, “Comets” Gases, Ices, Grains, Plasma”. Contributed papers will appear in a volume of Icarus. Papers dealing with cometary and asteroidal orbits appear in IAU Symp. 81, 1979 and with cometary grains and meteorites in IAU Symp. 90, 1981. Proceedings of Workshops are: (1) “Experimental Approaches to Comets”, ed. J. Oro, 1978, Lunar and planetary Institute, Pub. 361; (2) “Modern Observational Techniques for Comets”, eds. J. Brandt et al., 1981, JPL Pub. 81-68, NASA.

The past triennium has seen an unprecidented increase in our knowledge and understanding of the solar system and, in particular, of the planets and satellites of the outer solar system. This epoch – 1 January 1979 to 31 December 1981 – has witnessed major spacecraft missions to Venus, Jupiter and Saturn by the United States and the launch of further missions to Venus by the Soviet Union.

An avalanche of discoveries pertaining to the satellite and ring systems of Jupiter and Saturn followed from the encounters of Pioneer 11 with Saturn, of Voyagers 1 and 2 with both Jupiter and Saturn, and from the passage of the Earth through the Saturn ring plane, all of which occurred during the triennium. The first comet discovery from a spacecraft also occurred during the same interval, a coronagraph experiment on the satellite P78-1 apparently catching a Kreutz sungrazer in the last hours before it impacted the Sun on 1979 August 30. Several successfully observed occultations of stars by the Uranian ring system, by minor planets, and possibly by satellites of Neptune and Pluto testify to efforts inspired by the Commission’s Working Group on Prediction of Occultations.

The light of the night sky includes several components which spread all over the celestial sphere. These light components are terrestrial (airglow), interplanetary (zodiacal light), galactic (integrated starlight, diffuse galactic light) and extragalactic (extragalactic background light). Thus the study of nature of each light source, covering large distance, is pursued in different fields of astronomy. However, the techniques of measurement for respective components are similar and the knowledge of other lights is indispensable even in the study of a particular component.

Following past practice, a number of authors have contributed reviews of their own field. These contributions have been edited by the President to reduce major overlaps and in some cases, due to space constraints, to reduce the length of the reviews. When possible reference numbers in the Astronomy and Astrophysics Abstracts are used. As editor, the President accepts responsibility for any shortcomings in the report.

The name of this commission was recently changed from “Parallaxes and Proper Motions”. These data are at this time indeed obtained mostly by the techniques of photographic astrometry, but so is the bulk of relative star positions. It is clear, however, that the nonabsolute determination of relative positions and data derived from them in narrow fields (which describes the scope of this Commission) is going to be carried out more and more also by nonphotographic methods, namely photoelectrically (Earth and satellite based) by interferometry (optical, radio, and speckle) and by direct imaging. This therefore creates considerable overlap with the subject areas and methods of a number of other Commissions, especially Commission 8, and it will be appropriate for Commission 24 in the near future to examine critically the overlapping areas of interest and to come to an agreement about the definition of the proper responsibilities of the individual commissions.

Most astronomical observers at some time become involved in photometric techniques even if the participation may be limited to a rough check of the brightness of an object for measurement at the telescope. The field is in fact so broad that much of the current work is more appropriate to the reviews of other IAU Commissions and it has become accepted that Commission 25 deals mainly with those subjects which are of common practical interest to photometrists and polarimetrists around the world. We are now at the beginning of a new stage, that of observation with space telescopes and it will be important to ensure that the transition to the new techniques of measurement is a smooth one. In our review, we restrict our discussion to stellar work, leaving to other Commissions the consideration of photometry and polarimetry of stellar systems, solar system objects and gaseous nebulae. We consider recent work concerning detectors, photometric and polarimetric systems, standard stars and sequences, catalogues of new material and related items of interest to observers. The reference numbering system of Astronomy and Astrophysics Abstracts is used where possible. We shall draw attention to some important conference volumes and to some major observing projects completed during the last 3 years and finally shall look briefly towards probable developments and future prospects for the times ahead.

Since the summer of 1979, more than 17 000 visual measures were made and have either been published or are being prepared for publication.

Couteau, using the 50- and 76-cm telescopes at Nice, obtained 984 measures and also discovered 207 pairs. Of these, 13% are closer than 0″.25, and 33% have separations smaller than 0″.5. Also at Nice, Morel made 300 measures with the 76-cm refractor and discovered 6 pairs.

With the enormous rise in publication costs, the space available for these triennial reports is becoming ever more precious, while the amount of research to be reported on becomes ever larger. Thus while my predecessors have used this introductory section to detail the symposia and colloquia held over the past three years, as well as other administrative matters, I have decided to omit this material (which is available elsewhere) in favour of maximizing the space available for science reporting.