Stellar photons for your retina

An atlas is a book of maps to find where things are. So this Photographic Atlas of the Stars is to find your way about in the starry sky. The idea is that you go outside on a dark night - no moon, no light pollution - and you look up and around with your eyes, or at most a pair of binoculars. And this is what meets your eyes.

So this is a "people's atlas" of astronomy, intended to represent what you see. In this atlas, what you see is what you get - if you are in a dark site. If you live in a city centre and can see just the brightest stars, this will demonstrate what you are missing - take the atlas on holiday (to the country, not a brightly lit resort).

The core of the book consists of 45 colour photographs taken by H. J. P. Arnold with a 35 mm Nikon SLR camera, a good but not a specialised sort of camera, built for the purpose of faithfully recording what you see. The photographs are faced by their keys, black and white maps, drawn by Paul Doherty on to negative prints from the photographs (black stars, white background). In a further two pages, Patrick Moore describes the appearance of the sky in this region, noting coloured stars, identifying double and variable stars, naming nebulae, clusters and galaxies, and tabulating numerical data.

The coordination of the three collaborators was good. The maps are excellent matches to the photographs, with account taken of the distortion of the camera. However, the narrative and tabular material is not exactly matched with the maps, with some stars noted in the tables but not identified on the maps.

The effort that has gone into this work is remarkable. Just three of the photographs were taken from Europe (one from Britain, and two from Portugal).

Arnold travelled far afield to dark observing sites for the others: South Africa, New Mexico, Alice Springs. The set of photographs must have been made over an extended period of years, because there is only one photo in which I found a solar system object, Comet Hyakutake: Arnold waited not only for skies clear of clouds, but also for constellations free of planets. I guess there must be some asteroids somewhere, so if you notice a small "star" that is on the photographs but missing from the sky, it might be an asteroid that has moved. On the contrary, if you notice a new star in the sky that is not on the photographs, it could be a planet, or you could be on to something big.

The photographs are made with colour film. In the photograph of the constellation Orion, Rigel is white-blue, Betelgeuse is orange, similar to Aldebaran in the nearby constellation Taurus. I say that Rigel is white-blue: the centre of its image is white - the colour film is saturated by the star's brightness and overexposed colour film is white. But the star's fainter halo is blue. The range of colour in the sky is not large and the photographs are correspondingly subtly coloured. This accords with experience. Patrick Moore's text helps you notice what colour there is, and explains how this corresponds to the different temperatures of stars.

Historically there has been a temptation to over-ornament sky atlases. An engraver or artist sees the arrangement of different size spots on the paper and cannot resist decorating the sky with mythological figures. It is well-intentioned and certainly makes the page more interesting to glance at, but less convenient to pore over. So plain is good.

Do we want to have pictured only what we see? By contrast to Arnold's atlas, David Malin's compilations of spectacular colour astrophotographs have extended our colour vision by darkroom wizardry and the use of a Pounds 10 million telescope, so we can see in his photographs of the universe what we cannot see with our eyes. That is a mind-expanding intellectual adventure but a sedentary armchair experience - by no means a bad thing, but completely different from going outside in a woolly hat and mittens, in the dark and experiencing the stellar photons, centuries old, hitting your retina. Even though the Photographic Atlas is nicely produced and you will not want to mishandle it, take it out at night and cross check against the sky; use its help to experience the real thing.

Paul Murdin is head of astronomy, the Particle Physics and Astronomy Research Council.