On behalf of The Royal Astronomical Society of Canada, I wish to thank the con­tributors to the 1984 observer’s handbook (see the inside front cover). In particular I wish to welcome Fred Espenak (Eclipses), Robert Garrison (The Brightest Stars), and William Herbst (Galactic Nebulae) as new contributors. The latter two replace Donald MacRae (David Dunlap Observatory) and René Racine (Canada-France- Hawaii Telescope) respectively, both of whom have provided valuable support to the handbook over several years.

Several revisions and additions have been made for 1984. The table of physical elements of the solar system has been updated using the IAU (1976) system of astronomical constants (U.S. Naval Observatory Circular #163). Joseph Veverka has expanded the table on planetary satellites. The section on time has been revised, partly in response to the introduction of Terrestrial Dynamical Time in 1984. Thanks to the initiative of Fred Espenak, the section on eclipses has been considerably expanded. The magnitude limit for total lunar occultation predictions has again been changed (from 6.0 to 5.0) in recognition of the availability of more extensive predic­ tions for experienced observers from other sources, and to give more emphasis to lunar graze events. Blyth Robertson has revised the section on meteorite impact sites. Janet Mattei has again provided new material for the variable stars section; this year it includes a description of the photoelectric photometry observing program of the AAVSO. Anthony Moffat has included some information on stellar associa­ tions in the star clusters section. William Herbst has revised the list of galactic nebulae to include more objects in the southern sky.

In addition to the regular contributors, several other individuals have provided ideas and support. I particularly want to thank Randall Brooks (St. Mary’s Univer­ sity) for providing twilight times, information on an occultation by Neptune, and the base map for the path of Pluto. Leo Enright (Sharbot Lake, Ont.) provided input on the accuracy of the sidereal time equation.

The observer’s handbook could not exist without the strong, voluntary support of its twenty-four contributors and the provision of pre-publication material from The Astronomical Almanac by both the Nautical Almanac Office of the U.S. Naval Observatory and Her Majesty’s Nautical Almanac Office of the Royal Greenwich Observatory. Additional support is provided by Rosemary Freeman, Executive- Secretary of The Royal Astronomical Society of Canada, and by the Department of Physics, Acadia University, Nova Scotia. In the latter instance, I especially wish to acknowledge the careful preparation of the lunar occultation tables, in both this and the previous two editions, by Julia Melzer.

Comments and suggestions should be directed to the Editor (address on the inside front cover). Good observing quo ducit Urania!

Roy L.Bishop, Editor

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