Coming to grips with Halley mania

Press, 8 February 1986, Page 20

Coming to grips with Halley mania

Halley: The Once In a Lifetime Comet. By David and Caro! Allen. Unwin Paperback, 1985. $14.95. Observing Halley’s Comet: The Complete Guide to the Comet from Southern Latitudes, 1985-86., Seven authors from Astronomical Society of N.S.W. Unwin paperback, 1985. $14.95. (Reviewed by John Hearnshaw)

New Zealand, along with other countries in the Southern Hemisphere, will shortly be in the grip of Halley mania. The famous comet swings past the sun on February 9, and will be visible on its outward journey from late February. The prime viewing season will be early April. The media and the travel industry will be cashing in on this predictable celestial event and reaping a rich bonanza. At least 20,000 northern hemisphere tourists are expected in New Zealand to view this once-in-a-lifetime comet. A large number of books have been written on the comet for the layman — this reviewer is aware of eight such publications, and no doubt this is only a tiny fraction of the total. First some basic facts: there have been at least 25 and possibly 28 previous recorded sightings of Halley’s Comet, at Intervals of every 76 years stretching back to a possible Chinese observation in 467 B.C. The visibility of the comet, however, varies widely at each reappearance, as a result of the relative positions of the sun, the comet and the earth over a time span of about six months.

The 1986 appearance of the comet will be the least favourable since 316 8.C., since the comet will be on the far-side of the sun during February. It therefore seems very likely that Comet Halley will be a considerable disappointment for all those hoping for a celestial spectacle comparable to that of May, 1910. The least optimistic predictions are that Comet Halley will never be visible to the naked eye in 1986, even at its brightest; the most favourable

are that it will only be seen without binoculars or a telescope by those observing away from the glare of city lights who know where to look in early April, when the moon will be dark. Those with binoculars or a telescope should, of course, be well rewarded, and provided the media do not raise expectations too high, then amateur observers in New Zealand should not be disappointed. Scientifically Comet Halley’s return is an event of considerable importance, especially in view of the close rendezvous by the Giotto spacecraft with the comet, and of the intensive observing campaign using large ground-based telescopes. Regrettably, other astronomical events and discoveries of equal or greater scientific importance are usually given less media attention than Comet Halley is receiving.

For those still enthused by the Halley ballyhoo in spite of my caveat, here are two short books to inform and guide you. Both are written for the cometary novice who wishes to join in the fun and catch a sight of the comet and talk knowledgeably about it with his (or her) friends. Each is, however, quite different in scope. David Allen is a professional British astronomer currently working in Australia. With his wife he has written a popular and very readable account that nicely blends the scientific aspects of comets with the history of past sightings of Comet Halley and of the work of Sir Edmund Halley three centuries ago. For those who want a clear and simple account that demands 'no previous scientific knowledge from the reader, then this book is highly recommended. The work is sadly marred by the poor quality of the sky charts that purport to give the comet’s daily position against the background of stars. I defy all but the most persistent or competent of observers to find the comet with these woefully inadequate sketches. Fortunately the second book reviewed here more than makes up for the one deficiency of the other work. “Observing Halley’s Comet” has been compiled by seven members of the New South Wales Astronomical Society. It is easily the best guide I have seen for those who want to know where and when to look. The star charts are excellent, and for those with equatorial telescopes, there is a table of co-ordinates. There is practical advice on how to observe, for both visual and photographic work, and the technical information should satisfy many amateurs who already have a basic knowledge of astronomy. “Observing Halley’s Comet” is no more than an informative observer’s guide. For those who both wish to observe the comet, and to have a general knowledge of cometary history, science, culture and folklore, the purchase of both books is advised.