Observing Safely

The Greatest Spectacle in the Whole of Nature

Observing An Eclipse Safely

Looking at the partial phases of a solar eclipse is just as dangerous and carries the same risks as looking directly at the sun at any other time. It is important to emphasise that while any part of the bright solar disk is visible you should not look at it directly. Great care must be taken to protect your eyes from damage when observing the partial phases. When all of the sun has disappeared in a total eclipse it is safe to look directly without eye protection but it important to be prepared for the bright sun returning and look away immediately.

Special filters are available, usually in the form of cardboard framed spectacles, and they must always be used with great care. Before use, it is important to check that the filter material is not damaged, if it is, then throw it away and don’t use it. Filters are generally one of two types. Those that appear silvery are made from mylar, are particularly fragile and can tear easily. Others use a thicker, black plastic material and are more robust but can still be scratched. Even though the spectacles have ear pieces, they should still be held firmly with both hands as they can easily fall or blow off in the slightest wind. Never move around while using a filter as you can knock other people over, damage equipment or trip up. And don’t look for too long, you won’t actually be able to see the sun moving so it’s better to look for a few seconds then look away for a few minutes. When you look back you will then notice how the eclipse is progressing.

Always use a filter that has come from a reputable supplier and make sure that it is marked as approved for direct solar use with an appropriate safety mark. Over the years we have seen people looking through old negatives, X-ray plates and a host of other improvised devices. The message is always the same – don’t use them, your eyesight is too precious to lose. Don’t let the eclipse be the last thing you ever see

The safest way to observe the partial phases of an eclipse is to use a projection method. A small hole, made with a sharp pencil, in the middle of a piece of card will act as a pinhole camera and will project a small image on to another piece of card held a metre or so away. Don’t use a pin to make the hole as this is too small and you get very little light through. And don’t use a shiny card to display the image as it may reflect too much light and dazzle you.

Simple pinhole cameras

The size of the image can be increased by propping up the screen card further away but as the image gets bigger it gets fainter because there is a fixed amount of light coming through the pinhole. Remember to always look at the image on the screen card – never look through the pinhole or directly at the sun.

A much better method is to use a small flat make-up mirror or something similar. Tear a thumbnail-sized hole out of one side of an envelope and put the mirror inside the envelope with the centre of the mirror roughly in the middle of the hole and fold the edges of the envelope over the back of the mirror.

The miiror in the envelope method

Now stand facing towards the sun and, using your mirror in the envelope, reflect it on to a shaded wall or other improvised screen about 10 metres or so away. Take great care to never allow anyone to look at the sun in the mirror and never shine the reflected light into anyone’s eyes.

The safest solar projection method

For best results, try to reflect the image back in the direction of the sun to cut down on distortion. The further you are away from the screen, the bigger the image becomes, but, as we have seen before, the image gets fainter. A white screen, placed at right angles to the reflected beam is ideal. If you can arrange to fix the mirror in some way then the image will be stable enough for you to draw round the image on the screen and you can build up your own personal record of your eclipse.

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