Travel The Eclipse: Capturing a total eclipse

How can you view the dramatic event safely and get a photograph?

Eye safety cannot be stressed enough when photographing the Sun. The sphere of bright yellow that we see from Earth is called the photosphere. With a temperature of 5,500C, it is as bright as looking directly at the light from an arc welder. When a total eclipse occurs, the Moon blocks out most of this bright light only for the few minutes of totality. If you are along the true line of totality you can look directly at the sun in complete safety only during the few minutes in which the total eclipse occurs.

In fact, you would need to be only a fraction off the line of totality and you would do your eyes serious damage. The problem occurs when our eyes are exposed to infrared and ultraviolet radiation. These are capable of damaging both the lens of the eye and, more importantly, the retina, the eye's screen. As the retina has no pain receptors, we get no warning of impending danger until it's too late.

The only completely safe way of looking at the Sun is by projection. A pair of binoculars or a telescope pointed at the Sun reflects its image on to a piece of white card, held at the correct distance as to make the projection as sharp and focused as possible. A simple and cheap way to do this is to take two large pieces of white card and attach one piece on to the end of a long, flat surface. Punch a small, neat hole in the middle of the card and then take the other piece and move it backwards or forwards until you can clearly see the projected image of the Sun. As long as you move with the Sun, you will be able to watch the whole event in absolute safety.

Alternatively, there are some perfectly safe sun-viewing glasses available. These are all superior to projection in terms of image quality and are easy to use (see below for suppliers). And be especially vigilant if there are children about.

Photographing the eclipse

First mount your camera on a tripod and choose an appropriate lens. A 28mm lens should allow you to photograph the whole eclipse without moving the camera but the Sun will look extremely small. It will be excellent if you want some foreground detail such as a building or natural vista in the picture.

With the standard 50mm lens the Sun will appear as a small circle or dot. Ideally, a 200-300mm lens will give a good image and, depending on your position, may even allow some other details in the picture, such as the tops of buildings and trees. Tape your lens focusing-ring at infinity so that it can't move. You will need neutral density (ND) filters to a value of at least 5.0 or 6.0 or a material known as Mylar to tape over the front of the lens and protect the camera. Neutral density filters reduce only visible light (remember, the danger to the eyes is ultraviolet and infrared radiation, so don't look through the camera without additional eye protection). Only during the total eclipse can the sun be photographed without ND filters.

Use 100ASA colour print or slide film. Set the aperture on the lens to a mid-range setting such as f8. During the partial stages of the eclipse, with the ND filters on, bracket your exposures using the camera's shutter speed dial. Initially, try a shutter speed of 1/250th of a second and bracket one speed either way for each part of the eclipse. A little practice beforehand is a good idea.

When totality occurs and the filters are off, take a series of pictures at the following shutter speeds; 1/1000th, 1/500th, 1/250th, 1/125th, 1/60th, 1/30th right down to 1/2 a second. These settings should give good pictures of various phases of the total eclipse, highlighting phenomena known as Bailey's Beads, the Diamond Ring, the Prominences and the Inner and Outer Corona.

The eclipse is a spectacle with quite a buzz and you don't want to miss out on all the excitement because you're fiddling with dials, so make sure that you have a small torch handy (for when the sky becomes dark during totality). But don't shine it at other people; nothing annoys astronomers more. Similarly, on automatic cameras, make sure the flash is turned off.

Take plenty of tea or water with you, some snacks to eat and something to provide you with shade (if the weather is nice it will be a long morning). Lastly, find yourself a travelling companion. One should never enjoy such magic without the company of friends.

Finding Out More

Good technical information is available at the following web sites:

http://www.eclipse.org.uk http://sunearth.gsfc.nasa.gov/ eclipse/eclipse.htm http://sunearth.gsfc.nasa.gov/ eclipse/TSE1999/TSE1999.htm

Full astronomical data can be found at : http://www.ast.cam.ac.uk/nao/ http://www.ast.cam.ac.uk/ eclipse99

Among the best books on the subject that we have found are:

The RGO Guide to the 1999 Total Eclipse of the Sun by Steve Bell (Royal Greenwich Observatory, pounds 5.99)

Eclipse '99: Capture it on Film by HJP Arnold (IOP publishing, pounds 5.95)

Specialist equipment, viewing glasses and filters can be purchased from:

Broadhurst Clarkson & Fuller Ltd, Telescope House, 63 Farringdon Road, London EC1M 3JB (0171-405 2156)

David Hinds Ltd, Unit 34, The Silk Mill, Brook Street, Tring, Herts HP23 5EF (01442 827768)

Venturescope, The Wren Centre, Westbourne Road, Emsworth, Hampshire PO10 7RN (01243 379322)

Eclipse99 Ltd, Belle Etoile, Rue du Hamel, Castel, Guernsey GY5 7QJ (01481 64847)

More details and suppliers can be found in Astronomy and Sky & Telescope magazines.