J. Brit. Astron. Assoc., 108, 1, 1998, p.47

The Aurora: An Introduction for Observers and Photographers

by Jim Henderson & John MacNicol

Crooktree Images (Crooktree, Kincardine O'Neil, Aboyne, Aberdeenshire AB34 4JD), 1997. ISBN 0-952-94341-7. Pp 80, £14.99 (pbk).

reviewed by D. A. R. Simmons

This splendid collection of auroral photographs is compiled by Jim Henderson and John MacNicol, the former a professional photographer and the latter a software support analyst working in the international oil exploration industry. The majority of the photographs are the results of Mr Henderson's personal expert endeavours, but the collection has been augmented with selected pictures taken mainly by amateurs around the world. His co-author has provided an account of some of the geophysical and solar factors involved in the generation of auroral events, in a chapter entitled 'Aurorae (The cause of the effect)'. The book, which is intended as an introduction for would-be observers and photographers of the aurora, contains a very practical section on the choice of cameras, tripods, films and other accessories. More importantly, it gives good practical advice and hints on how these can be used effectively to secure good photographs. It also deals with problems such as exposure times, condensation and camera stability. This is an excellent and comprehensive account that reflects the author's close involvement with his subject. The only thing that might be regarded as missing is 'bracketing', a technique in which the estimated exposure is bracketed with a shorter and a longer one. This improves the success rate and is a good way to acquire a working knowledge of the exposures required for aurorae of different brightness. It is, however, extravagant with film.

The collected photographs are, for the most part, quite superb - some highly artistic (plates 1 and 58); some quite stunning (plate 10); some scientifically interesting (plates 9 and 16); some simply beautiful (plates 59 and 69) and a few, all four of these in one (the frontispiece). In view of the excellence of the photographs, it is disappointing that the authors did not take the opportunity to relate the observed photographic features to the underlying basic geophysics - for example, plate 9 shows a type a arc with a lower green border and an upper red border that has been changed to purple by admixture with blue N2+ emission. The single ray has a blue/violet colour from enhanced resonance excitation of the N2+ emissions due to irradiation with solar ultraviolet light. The junction of the purple and violet regions indicates the position of the Earth's-shadow-line in the auroral ionosphere. Plate 14 demonstrates the nature of patches. These are fragments of an arc that have a higher flux of auroral electrons than the adjacent regions of the arc. Plate 23 is certainly a good example of a corona but also a classical auroral loop with its closed end toward the west; the 'peculiar black space' is simply the dark night sky photographed through this loop. There are quite a number of other instances where auroral morphology could have been correlated with the geophysics to give a better understanding of the photographs.

The section on the Aurorae (The cause of the effect) gives a good account of solar and geophysical events related to auroral production. It is quite detailed but not too detailed - a commendable balance for an introduction to the subject. Unfortunately, some of the descriptive accounts are inaccurate and misleading. The statement is made on page 75 that the auroral ovals are seen around 'the north and south magnetic poles'. They are, in fact, eccentrically displaced on the north and south geomagnetic poles in the direction of the midnight sector (or the magnetotail). Similarly, on page 76, we find that the arc is 'centred in the direction of the magnetic pole' whereas all the auroral types that feature in this photographic collection are orientated in east-west geomagnetic alignment centred on the geomagnetic pole. There are other such inaccuracies. Despite these limitations, the overall impression of this book is that it is a splendid and colourful production with lots of practical advice. It therefore succeeds in its primary objective as an introduction to the aurora for observers and photographers. It also seems certain that it will appeal to everyone with an interest in this most beautiful of natural phenomena, and at £14.99, it is very good value for money.


Alastair Simmons is an active member of the Aurora Section who visits the high arctic most winters to study the aurora.

Return to Journal 1998 February contents page