David Galadí-Enríquez
Coordinator of the Scientific and Advisory Committee for the Eclipse Trio and lecturer in the Department of Physics at the University of Córdoba
You must protect your eyes when observing the Sun’s disc. A solar eclipse is dangerous not because it is an eclipse, but because it involves the Sun. Any direct gaze at the Sun’s disc when it is not obscured requires protection. You may only – indeed, I would say you must – look at the Sun without protection during the few seconds that the total phase of the eclipse lasts, whilst the Sun is covered by the Moon. From locations where the eclipse is not total but partial, there is never a safe time to look at it without protection.
Only certified eclipse glasses (ISO 12312-2) provide safe protection. Any other method is unsafe and must be avoided. There is no need to wear the glasses the whole time whilst watching the partial phases of the eclipse. It is enough to look at it occasionally, and in the meantime, observe all the other things happening around you: changes in temperature, changes in lighting, in the shadows…
You can set up additional experiments based on the pinhole or ‘camera obscura’ effect: project the image of the partially eclipsed Sun using objects with holes (slotted spoons, sieves, cardboard with holes punched in it, gaps between the leaves of a tree, etc.). It’s safe, spectacular and great fun.
Photographing a solar eclipse is a complex task that is only within the reach of experienced photographers. Many of them will take spectacular photos and videos. The general public would be well advised not to attempt to capture the phenomenon using basic equipment such as mobile phones and without prior experience: the results will be poor and they will miss out on the personal experience of witnessing the eclipse. We must focus our attention on the stars, the universe and our surroundings, rather than on a mobile phone with which to take a poor-quality photograph.
Anyone planning to travel should do so in good time – ideally with a day’s buffer – and should also avoid setting off immediately after the phenomenon has ended, as there will be major traffic jams.