the observer’s handbook for 1975 is the sixty-seventh edition. I wish to thank all those who assisted in its preparation: those whose names appear in the various sec­ tions, those mentioned below, and especially my editorial assistant John F. A. Perkins.

There has been some rearrangement of material in this issue; both new readers and readers of past issues should skim through and find out “where everything is”. Also in this issue, metric units have been introduced wherever possible. There is a new section on “Impact Craters”, so that readers can find their way to visit some of these spectacular features. The handbook is continually being expanded and improved. This year, I extend a warm welcome to three new contributors—P. Blyth Robertson, who pre­ pared the section on impact craters, Brian G. Marsden, who supplied the material on periodic comets, and Janet Mattei, who as the new Director of the A.A.V.S.O. supplied the predictions of Algol and of other variable stars. At the same time, I want to take this opportunity to thank Margaret W. Mayall who before her retire­ ment as Director of the A.A.V.S.O. supplied these predictions for many years.

Once again, special thanks go to Leslie V. Morrison and Gordon E. Taylor, H.M. Nautical Almanac Office, for the predictions of total and grazing lunar occul- tations and of planetary appulses and occultations; to Maude Towne and Isabel Williamson for the tables of moonrise and moonset; to the David Dunlap Observa­ tory and Erindale College, University of Toronto, for financial, technical and moral support. Finally, my deep indebtedness to H.M. Nautical Almanac Office and to the American Ephemeris is gratefully acknowledged.

John R. Percy