I Historical.- Amateur Astronomy from Its Origins to Camille Flammarion.- Camille Flammarion (1842-1925): Founder of the Société Astronomique de France.- The Historical Contribution of Amateurs to the Study of Double Stars.- Twentieth-Century Amateur Astronomy.- Criteria for Identifying an Astronomer as an Amateur.- Johannes Hevelius: Polish Seventeenth-Century Brewer and Astronomer.- Eugène Antoniadi (1870-1944) and Planetary Observation.- Investigating Astronomy''s History.- Charles Boyer and the Rotation of Venus.- The Amateur and Eclipsing Binary Stars.- Amateur Astronomy in Poland: Past and Present.- Giovanni Battista Lacchini: An Amateur Astronomer from Italy.- The Instruments of H.E. Dall.- Roberts of Lovedale and Eclipsing Binary Stars.- Seventeenth-Century Solar Observations: Fundamental Results with Amateur Instruments.- Sailors and Astronomy.- The Map of the Heavens at the Chateau de Saint-Jean-de-Chepy.- Amateur Astronomy in France, 1789-1830: Two Examples.- Some French Amateurs of the 2nd Half of the 19th Century.- Comet Halley in 1910 in Franche-Comté: or Collective Memory at Fault.- A Renowned, Yet Forgotten Astronomer: Marcel de Kerolyr.- Historical Session: The Contribution of Amateurs to Astronomy, Yesterday and Today.- II Observational Methods.- Amateur Astronomers and the IAU Central Bureau for Astronomical Telegrams and Minor Planet Center.- Contributions of Amateur Astronomers to Variable-Star Observing.- Observations of Comets, Minor Planets and Meteors in Japan.- Amateur Astronomers'' Contribution to the HIPPARCHOS Programme.- The S. A. F. Double Star Section''s Contribution to the INCA-HIPPARCHOS Programme.- Working with Amateur Astronomers.- Amateur Astronomers and the Hubble Space Telescope.- The T.60 Operation at Pic du Midi.- The Effects of Light Pollution on Amateur Astronomy.- An Amateur CCD Camera.- A Spectrograph for the T.60 at Pic du Midi.- Using an Image-Intensifier in Astronomy.- Amateur Polarimetric Research.- Searching for Variables, and Constructing a Slit-less Spectroscope.- Solar Spectroscopy with a CCD.- Obtaining Extraterrestrial Dust by Balloon Probes.- Making a Telescope Mirror.- Searching for Comets.- Achievements in Astronomical Video Data Collection.- Video Grazing Occultations.- An Improved Method of Photographic Measures of Double Stars.- The Scientific Merit of Amateur Astrophotography.- Reduction of Variable-Star Observations Using Basicode.- Image Digitizer.- "Comet" Software.- Refining the Orbit of Visual Double Stars.- Reliability and Accuracy of Astronomical Observations by Amateurs.- Trying to Reduce Errors in Visual Estimates of Variable Star Magnitudes.- III Observations and Results.- Photographic Observation of Stellar Occultations.- Studying "Luna Incognita": The Region Near the South Pole.- Asteroid and Cometary Occultations.- Astrometric Measurements of Rarely-Observed Minor Planets.- Video Recordings of Asteroidal Occultations.- Space Exploration of Comets and the Evolution of Amateur-Professional Cooperation.- The Contribution of Amateur Astronomers to Cometary Observation.- New Method of Statistical Analysis of Cometary Light-Curves Applied to P/Halley.- P/Halley: The Disconnection Event of 1986 April 11.- A Study of Disconnection Velocities in the Plasma Tail of P/Halley.- Analysis of the Light-Curve of Comet P/Halley in 1985-1986.- New Trends in the Discovery of Comets by Amateurs.- Amateur Astronomers and the Recovery of Periodic Comets.- Shape and Frequency of Outbursts of P/Schwassmann-Wachmann 1.- Astrometry of Comet Halley.- Observation and Analysis of Comet Tails.- Photometric Analysis of the Solar Corona on 1984 November 22/23.- Chromospheric Eruptions Observed with a Wide Slit.- Amateur/Professional Cooperation in 2 Solar Studies.- The IOTA Expedition Results from the Total-Annular Eclipse in Gabon, 1987.- Meteor Studies.- The "Sonate" Campaign.- Two Solar Observation Programmes.- Long-term Monitoring of Solar Activity by Amateur Astronomers.- The Moonwatch Program: A Model for Amateur Contributions to the ISY.- Study of Variable Stars.- The Contribution of Amateur Astronomers to the Study of Variable Stars.- Professional/Amateur Cooperation in the Study of Variable Stars as Illustrated by the Fourth Edition of the GCVS.- Amateurs and the Search for Supenovae.- The U.K. Nova/Supernova Search Programme.- GEOS -- Groupe Europeen d''Observations Stellaires.- GEOS Results for PX Cephei.- The French Network for Observing Comets and Small Solar-System Bodies.- Amateurs'' Contribution to the PHEMU85 Campaign Observing Mutual Phenomena of Jupiter''s Satellites.- Wanted: An International Jovian-Satellite-Phenomenon Centre.- The European Section of IOTA: Scientific Programme Coordination and Results.- The Role of the Amateur in Modern Astronomy.- IV Popularization.- Meeting the Public: Popular Observatories.- Comet Halley: A Media Event.- A Planetarium for Astronomy.- Astronomical Publications.- Problems in Publishing a Popular Journal in a Small Country.- Methods of Popularizing Astronomy in Various Countries.- Opening the Sky to Everyone.- Interesting Business in Astronomy.- Preparing Astronomical Videotapes.- Transmission of Astronomical Data and Information by the A.F.A. Videotext System.- The Solar System Promenade.- The Open Sky Underground.- Teaching Astronomy in Schools.- Teaching Astronomy and the Vital Role of the True Amateur.- Astronomical Education in Poland.- Astronomy and Computing in Spanish (Aragon) High Schools.- The Planetarium at the Palais de la Découverte.- The Starlab Mobile Planetarium in the Mid-Pyrenees.- The Planetarium at a School in Nice.- The Planetarium as a Medium for Teaching Astronomy.- Twenty Years of the Japan Amateur Astronomers'' Convention.- Astronomy in the Big Apple.- The Activities of Astronomical Clubs.- The Flammarion Astronomical Society of Montpellier.- A Decade of Organized Work in Venezuela.- The Bochum Observatory.- The Triel Observatory.- The Bruno-H.-Bürgel Observatory.- The Strasbourg Observatory.- Feeding the Five Thousand.- Efforts by the Instituto de Astrophisica de Canarias to Publicise Astronomy.- Tailor-Made Messages: Astronomical Information for Diverse Audiences.- The Role of the Observatoire de Paris, Meudon in Providing Astronomical Information.- Observations -- Concluding Remarks.- International Astronomical Union -- Colloquium 98 General Session.- List of Participants.