Safety First

No book about observing the Sun, whether eclipsed or not, would be fit for publication without mentioning the dangers of solar observing. These dangers were hammered home to me, many years ago, when the English observer J. Hedley Robinson damaged his eyesight while observing the Sun. I would not have believed such an experienced observer could have come to harm in this way, but he did. He was using an experimental filter he had devised to allow comfortable solar observing. However, he had tragically underestimated the amount of infra-red radiation the filter was letting through. The Sun looked pleasantly dimmed visually, but your eyes cannot see in the infra-red. Hedley became aware that his eye suddenly felt uncomfortably hot and instinct made him pull away. His vision in that eye was never the same. The eye is not equipped with pain sensors and so even when damage is being done to the retina it is not immediately apparent.