the observer’s handbook for 1981 is the seventy-third edition. On behalf of myself and the Royal Astronomical Society of Canada, I thank all those who have contributed to its production: the contributors listed on the inside front cover, and my editorial assistant Paul Ford.

Special thanks are due to Helen Sawyer Hogg for her unfailing interest and helpful comments. Ian McGregor kindly previewed the 1981 sky for me in the Star Theatre of the McLaughlin Planetarium. Alan Dyer provided the extensive new version of Messier’s catalogue, as well as his list of the 110 finest NGC objects. Brian Marsden provided ephemerides of a score of bright asteroids, making the asteroids section considerably more complete and rational. Doug Welch drew the maps of the paths of Uranus, Neptune and Pluto. Terence Dickinson, David Dunham, Ken Hewitt-White and Walter Scott Houston provided valuable advice on a number of points.

As always, the R.A.S.C. National Council, the editor Lloyd Higgs, and the executive secretary Rosemary Freeman have given me their cheerful support and assistance. The handbook also benefits greatly from the direct and indirect support of the Department of Astronomy and Erindale College, University of Toronto.

The handbook is particularly indebted to H.M. Nautical Almanac Office (U.K. Science Research Council) and to the Nautical Almanac Office, (U.S. Naval Observatory). I am especially grateful to Leslie Morrison and the Occultation Section of H.M.N.A.O. for providing the wealth of information on total and grazing lunar occultations, and to LeRoy Doggett of the U.S. Naval Observatory for pro­ viding proof pages of the American Ephemeris in advance of its publication.

I hope the observer’s handbook serves you well. If you have comments or suggestions, let me know. Good observing!

John R.Percy, Editor