The dark night sky is rapidly being lost throughout the world due to wasted outdoor night lighting. Following warnings by astronomers and environmentalists, many communities are acting to preserve the night sky by enacting outdoor lighting codes. Here we briefly recount the history of codes and outline the essential elements of an effective code. Additional information, including a handbook on how to write a good outdoor lighting ordinance, is available from the International Dark-Sky Association web site, www.ida.org.

The plan for modification of public lighting in Frosinone, in accordance with the rule for the limitation of light-pollution and power consumption, is summarized. The energy saving obtained is 40% per year, equivalent to over US$222,000.

Sky glow was measured in the Netherlands in 1992 and in 1997. The 1992 measurements were photographic surveys, assessed in the Netherlands and in Japan, whereas the 1997 measurements were limit-star assessments. In all cases, the number of measurements was very small. The three sets of data are compared. The sky glow differs considerably over the country and during the night; there are no systematic differences between the results for different epochs and assessment methods. For measurements that allow conclusions that can be used in national policy making, the samples must be very much larger.

As in any developed country, light pollution is a serious problem in Quebec. However, a specific cultural and economical situation forces us to use new tactics when it is time to discuss this problem. As an example, using energy loss as an argument against light pollution is very inefficient since the electricity is cheap (US$0.04/kWh) and clean (hydroelectricity). On the other hand, using the negative ecological impacts of light pollution appears to be the most effective way to create awareness in the population.

This paper summarizes the change of astronomical observing conditions since 1986 at Huairou Solar Observing Station. Our results from 1988 to 1999 are as follows: quantitatively, stray light has increased and visibility has decreased; qualitatively, the seeing condition has become worse.

The central European climate in Germany is not ideal for serious astronomical observations. Increasing light pollution hampers thousands of amateur astronomers and millions of people from seeing starry skies and the Milky Way.

To study the sources of light pollution, we estimate the increase of light pollution in Osnabrück, a town of about 160,000 inhabitants located in northwestern Germany. We try to extrapolate these statistical data to Germany and discuss possible reasons for increasing light pollution though the energy consumption stagnates. Some enthusiasts of the German amateur association “Vereinigung der Sternfreunde” have formed a working group DARK SKY to exchange information on this matter. Finally, we present some activities to make the public aware of the problem.

In this paper we report the gradual change of the physical environment of the Bosscha Observatory in Lembang, Indonesia. From photometric observations carried out in 1982 through 1993 we found a slight increase of the aerosol content in the atmosphere. However, light pollution from the expanding city of Bandung (pop. 2 × 106; 10 km away at 600 m altitude below the Observatory) has produced significant light scattering at zenith distances greater than 55° toward the south.

In recent years Turkey has been losing the beauty of its night sky at a fast rate. The amount of outdoor lighting is increasing every day. University observatories at Ankara and Izmir are already irreversibly affected by light pollution. In this paper, work against light pollution in Turkey is outlined.

The current status of optical and radio astronomical sites in the Ukraine and the problems of preservation are briefly reviewed. The problems of light pollution and the influence of technology can be solved using scientific and engineering methods. However the main problem of preservation is the economic one of maintaining infrastructure.

The National Observatory of Athens (N.O.A.) will install a new, advanced technology 2.3-m telescope in Greece. A favoured location for the installation of the new telescope is the top of Mount Chelmos. We present preliminary results concerning the conditions at this site. It is found that the site has a quite dark sky, a good percentage of clear nights (about 60%) and very good seeing conditions.

We are proposing to operate a Network of Automatic Telescopes (ATN) for CCD imaging to conduct diverse astrophysical investigations and as a resource for science education. Coordinated utilization of telescopes at diverse sites provides the possibility of obtaining continuous photometry without diurnal interruption. We describe this project and discuss how it is impacted by light pollution, and conversely, how it might mitigate the growth of light pollution.

Northeast Utilities, the electric power distributor for Connecticut, has devised a plan to light the Arrigoni Bridge across the Connecticut River at Middletown. This paper descibes the plan and its impact on the surrounding region. The floodlights will affect migratory birds, and teaching and research at the nearby Van Vleck Observatory on Wesleyan Campus. Examples of bridges at other sites are also discussed, including the suspension spans of New York and San Francisco, that bear only tracer lights, or no lights at all.

The archives of meteorological satellites allow pre-selection of dry sites well adapted to astronomical observations (in the visible, infrared and millimetric ranges). The GSM (Grating Scale Monitor) technique then permits qualification of them as sites for future astronomical observatories. Such sites are found in new astronomical countries or in developing countries. At the same time, their protection from light pollution and/or radio interference has to be secured. In practice, once pre-selections are made, the governments of these countries ought to be alerted, for example by the IAU and/or the UN Office for Outer Space Affairs. The local site testing through GSM should be carried out in cooperation with scientists of these countries under the umbrella of the IAU. This could be an approach to help introduce astronomy and astrophysics into developing countries.

Attention is drawn to aspects of aviation that have a detrimental effect on ground-based astronomy. Depending on observing methods, science data can be influenced by an aircraft's emission of light, its thermal emission, exhaust products and condensation trail. Although these effects are mostly short-lasting for a given observing direction, they can be highly significant, and influence time-resolved astronomical observations. While the very young contrails can easily be recognized by ground-based or spaceborne observations, concern should also be given to older (hours, days) contrails, which have lost their characteristic linear shape. Contrails may grow to widths of tens of kilometers, and become almost indistinguishable from natural cirrus. As aviation increases, this may imply fewer photometric nights, in particular in the northern hemisphere, where by far the largest fuel consumption takes place.

The mass and number of Earth-orbiting human-generated space debris have increased steadily since the beginning of space flight. Recent voluntary measures for debris mitigation applied by space operators have not stemmed the increase. The debris hazard for manned and unmanned missions is still low, but rising. More effective but also more costly measures, such as selective deorbiting of used stages, will be necessary to avoid a run-away situation. Internationally agreed codes for debris management and control are needed to solve this global space environment problem.

The role and activities of COPUOS, the UN Committee for the Peaceful Uses of Outer Space, are briefly described.

Astronomical fields under observation are being increasingly crossed by satellites. Such crossings either leave a “trail” on a photographic or CCD image, or corrupt a photographic observation. Such trailing/corruption may render an observation useless for scientific analysis. There is also the much more serious problem posed by suggestions to put solar reflectors in space for Earth illumination, artistic, celebratory or advertising purposes and, by extension, to longer term suggestions of ways to utilise dark time rather than twilight time. It is only a matter of time until the solar reflector becomes proven technology. The time left for decisive action may be very short.

Space debris is the price which humankind must pay for entering space. And as this debris is dangerous in different ways, there must be ways to identify, catalogue, and predict the positions of, these cosmic bodies. That is why it is necessary to observe all artificial cosmic objects that are in space. One way of observing debris is by photometry. Photometric observations give light-curves from which one may deduce information about the position in space, the form, size, and other parameters of the object. Since 1975 a research group at Lviv Astronomical Observatory has been working at the problem of recording light-curves of different artificial cosmic objects. Four electrophotometers were constructed and developed. Many light curves of different artificial objects were measured with these electrophotometers. All light curves are collected in the local computer data bank and are available for use by anybody who needs such information.

Radio astronomy provides a unique window on the universe, allowing us to study non-thermal processes (e.g. galactic nuclei, quasars, pulsars) at the highest angular resolution using VLBI, with low opacity. It is the most interesting waveband for SETI searches. To date it has yielded three Nobel prizes (microwave background, pulsars, gravitational radiation). There are both exciting possibilities and substantial challenges for radio astronomy to remain at the cutting edge over the next three decades. New instruments like ALMA and the SKA will open up new science if the challenge of dealing with human generated interference can be met. We summarise some of the issues and technological developments that will be essential to the future success of radio astronomy.

For forty years radio astronomers have had access to frequency bands allocated by the International Telecommunication Union (ITU) - initially a League of Nations body (from 1919) and then a United Nations body (since 1945). Hard work and skilful negotiation by a handful of radio astronomers since 1959 have ensured viable access to scarce spectral allocations. There have been many battles won, some key battles lost. The next treaty conference of the ITU is in the year 2000.