On April 8, millions of people in Mexico, the United States and Canada will be able to watch an impressive total solar eclipse.

Astronomers are encouraging those in the eclipse's path to enjoy this rare spectacle one last time until August 2044, but only if they can do so safely. And sunglasses won't be enough to protect your eyes from this celestial event.

A total solar eclipse occurs when the Moon passes between the Earth and the Sun, completely blocking the face of the Sun.

Those in the path of totality, that is, in places where the moon's shadow completely covers the sun, will see a total solar eclipse. People outside the path of totality will be able to see a partial solar eclipse, in which the moon blocks only part of the face of the sun.

If your location only allows you to see a partial solar eclipse, you can still see some of the Sun's powerful light. And any glimpse of the sun's brightness with the naked eye is not only uncomfortable, but dangerous.

Why you shouldn't look directly at the eclipse

According to NASA, the only time the sun can be seen without eye protection is during the entirety of a total solar eclipse, or the brief moments when the moon blocks the sun's light.

Looking directly at the sun can cause blindness or impaired vision. During the total solar eclipse of 2017, a young person was diagnosed with solar retinopathy, caused by exposure to solar radiation, in ambos ojos tras ver el eclipse con lo que los medicos creían que eran gafas de eclipse que no complían las norms of security.

Solar retinopathy has no treatment. It may get better or worse, but it is a permanent condition.

Using eclipse glasses and solar finders

To view the eclipse, use approved eclipse glasses or a portable solar viewer. Alternatively, you can observe the sun with a telescope, binoculars or a camera with a special solar filter on the front, which acts in the same way as eclipse glasses would.

“You need solar eclipse glasses that comply with ISO 12312-2. There are many safe sellers on the Internet. There are many safe sellers online,” said Alex Lockwood, head of strategic content and marketing. integration for the Scientific Mission Directorate. NASA Headquarters. “We cannot stress enough the importance of getting a pair of certified and safe solar eclipse glasses to witness this annular event.”

Sunglasses will not replace eclipse glasses or sun visors, which are 100,000 times darker and meet an international safety standard.

The lenses of solar eclipse glasses are made of black polymer or resin infused with carbon particles, which blocks almost all visible, infrared and ultraviolet light, according to the Planetary Society. Sunglasses do not block infrared radiation.

For reliable manufacturers and distributors of eclipse glasses and filters for optical devices, including cameras and smartphones, consult the list compiled by the American Astronomical Society.

Put on your eclipse glasses before you look up, and remember to turn away from the sun before taking them off. Always supervise children who wear eclipse glasses to make sure they do not take them off when looking at the sun.

If you usually wear glasses, leave them on and place eclipse glasses over them or hold a portable viewer in front of them, according to the American Astronomical Society.

Do not view the sun through an unfiltered optical device (camera lens, telescope, binoculars) when wearing eclipse glasses or using a portable solar viewer, according to NASA. The sun's rays can continue to pass through the filter of your glasses or visor, given their concentration through an optical device, and cause serious eye damage.

It is also possible to use solder filters to observe the eclipse safely, as the international safety standard stems in part from the use of these types of filters to observe the sun.

Welding filters made of tempered glass or metal-coated polycarbonate and with a shade number of 12 or higher provide safe vision, but many consider shade 13 or 14 to be best and similar to using eclipse glasses, according to the American Astronomical Society. Just be aware that the sun will appear green instead of yellow-orange or white. These filters are not usually found on supply store shelves, but may be available online.

Adjustable welding helmets are not recommended because they may not darken quickly enough to see the sun.

Keep your glasses on

As long as the eclipse glasses or solar finders you use meet the ISO 12312-2 safety standard and are not broken, scratched or damaged in any way, they do not “expire” and can be used indefinitely. Plus, there is no time limit to see the sun with them.
Some eyeglasses and glasses have outdated warnings about wearing the glasses for more than three minutes at a time or recommend discarding them after more than three years, but this does not apply to glasses certified to ISO 12312-2, according to the American Astronomical Society.

Preserve your eclipse glasses and viewers for future eclipses by storing them at room temperature in an envelope or in their original packaging to avoid scratches.

Never use water, window cleaner, baby wipes, or other damp cloths to clean Eclipse glasses, as moisture may cause the cardboard frames to detach from the lenses. Instead, wipe the lenses carefully with a tissue or cloth.

Indirect observation of the eclipse

If you don't have approved glasses on hand, eclipses can also be viewed indirectly using a pinhole projector, like a hole punched in an index card. They work when you stand with your back to the sun and hold the card. The hole projects an image of the Sun in a crescent or ring shape onto the ground or other surfaces.

But never look directly at the sun through the hole.

Other pinhole projectors you may have on hand are strainers, straw hats, or anything with small holes. You can also raise your hands, spread your fingers, and cross them to create a waffle pattern. The small space between them will reflect the sun's crescent during a partial eclipse or a ring during the annular eclipse.

Are you next to a leafy tree? The small spaces between the leaves will reflect the phase patterns of the eclipse on the ground.