How to Watch the Solar Eclipse Safely, from a Vision Scientist.

I wrote about this during the last eclipse in 2017, now its time to update for this April 2024. How can you watch the solar eclipse without harming your eyes? What is so scary about a solar eclipse? Are there some special rays of light that only occur during the eclipse that make the Sun dangerous to our retinas? Actually, the answer to the last question is, no. So why is it dangerous to look at the eclipse with the naked eye? Read on for the answers.

The Sun can be bad for your eyes at any time, and the potentially damaging light from the Sun is always present. It simply gets easier to expose the retinas in the back of our eyes to this damaging light during an eclipse because the visible light does not seem very bright.  Normally, the full Sun is so bright that we never stare at it for very long. It creates instant discomfort, and we look away. Furthermore, when we look at the bright Sun, our pupils get very tiny to decrease the amount of sunlight that reaches the retinas in the back of our eyes. For those reasons, we never look right at the Sun and thus avoid projecting its burning image onto the parts of retinas that provide our most important central vision. 

When there is a Solar Eclipse, most of the Sun disc is blocked out, and the solar eclipse does not feel very bright at all. For that reason, it is easy to look at the ring of solar eclipse for many minutes. What you will not know though, is that some of the sunlight that you do not normally see is still radiating from the ring of Sun in view and that light is light that will literally burn and kill cells in your retina that you need for vision. 

The damaging light that you cannot feel or perceive is near infra-red light.. However, that near infra-red light can slowly burn and damage your retinas as you look at the Sun for many seconds and even minutes. It will happen with a solar eclipse, and also with the full regular Sun, but the intense brightness of a full Sun is uncomfortable and we look away. So the key to protecting your retinas and the retinas of your loved ones is to avoid watching the solar eclipse with the naked eye.

If you look at the Eclipse with regular sunglasses, that infra-red light, which you cannot see, is going into your very wide open pupils and overwhelming the photoreceptor cells that you need to detect visible light.  It is the near infra-red light that does this. The Sun emits a lot of this energy, you feel how it heats up your parked car, even in Winter?

You are best to watch a projection of the Eclipse through a card with a pinhole in it, or use a real lens, camera lens even, and let it project an image on another white card. Never look directly at an eclipse.

You can also buy special glasses made to watch the sun directly. They are so dark that you cannot even see bright fluorescent lights through them. They will also be marked to match an approved ISO standard set in 2015. Unless you know you have those kinds of glasses, you cannot be safe watching the eclipse directly. 

If you would like to make a simple solar eclipse viewer based on a design provided by NASA, then you can download the PDF instructions I made found at the following Google Drive link:

https://goo.gl/CDYG4J

or you can download from a Dropbox link here:

https://goo.gl/3F7yBC

All you need is a cereal box, a piece of white paper, tape, pencil, scissors, and aluminum foil. And one pin to make a pinhole in the foil.

Download my free PDF and enjoy full or partial solar eclipses safely.

Kenneth P. Mitton, PhD FARVO

Associate Professor of Biomedical Sciences

Eye Research Institute

Oakland University

Rochester Michigan.