the observer’s handbook for 1977 is the sixty-ninth edition. There are some changes and additions: the presentation of the configurations of Jupiter’s satellites, and of the sun’s selenographic colongitude, is different (see pg. 34); a diagram showing twilight and sidereal time has been added (pg. 12); the section on “Planets” has been rewritten and extended; and some “Suggestions for Further Reading” have been added. The index is now on the last page.

I wish to thank all those who have contributed to the preparation of the 1977 edition: those whose names appear in the various sections, those named below, and especially my editorial assistant, John F. A. Perkins. R. Bishop, L. Bogan and R. C. Brooks contributed the sidereal time diagram and many helpful suggestions. Terence Dickinson generously agreed to rewrite the “Planets” section; John F. Heard has again provided delightful introductions to “The Sky Month by Month”. Janet Mattei of the A.A.V.S.O. has provided information on variable stars, including Algol, δ Cephei and R Scuti—our “star for the year” (pg. 103). V. Gaizauskas pro­vided information on sunspots and on the eclipse in February 1979; J. Veverka checked the page of data on planetary satellites. I also thank Rosemary Freeman and Lloyd Higgs for their advice and help, and Carol Percy for assisting with some of the sections. The David Dunlap Observatory and Erindale College, University of Toronto, have once again provided financial, technical and moral support for the handbook.

Finally, my deep indebtedness to H.M. Nautical Almanac Office (especially G. M. Appleby, A. S. Dennis, Leslie V. Morrison, Gordon E. Taylor and Super- intendant Dr. G. A. Wilkins) and to the American Ephemeris is gratefully acknowl­edged.

John R.Percy