How to safely view the upcoming solar eclipse

By | March 28, 2024

People across the continental United States will witness a partial or total solar eclipse next month, but you should take precautions to avoid eye damage.

On April 8, the moon passes between Earth and the sun, temporarily blocking the sun’s light. During the sky alignment, the afternoon sky will briefly darken along a 100-mile-wide path that cuts through Mexico, part of the U.S. and a small portion of eastern Canada.

Those outside this so-called path of totality will be able to see a partial solar eclipse, in which the moon obscures only part of the sun.

To watch the spectacle safely, you can wear special glasses or build a pinhole projector. But don’t try to view the solar eclipse through normal sunglasses or use tools like telescopes to look at it – even if you wear good glasses – unless they are equipped with a special filter.

Here’s what you need to know.

How do you find the right eclipse glasses?

Glasses made specifically for viewing the sun provide the only safe way to view the solar eclipse directly.

“Eclipse glasses are very important to prevent photothermal damage to the retina, and not just any old pair of glasses – they should be eclipse glasses with the ISO 12312-2 filter,” says Dr. Nicole Bajic, a comprehensive ophthalmologist at Cleveland Clinic Cole. Eye Institute.

According to NASA, the glasses are “thousands of times darker” than sunglasses.

Without such precautions, viewing the solar eclipse can cause permanent eye damage.

“It’s called solar retinopathy, and it’s damage to very sensitive, complicated cells that make up the retina, which is the inside of the back of the eye, and that’s what converts light into electrical signals so we can see what we see ,” Bajic said. “And if we have sun damage to that tissue, we can get reduced vision and central blind spots in our vision.”

When and how to wear your glasses

The only safe time to view the solar eclipse with the naked eye is “when the moon completely obscures the bright face of the sun – during the short and spectacular period known as totality,” according to NASA, adding: “ You know it’s safe when you can no longer see any part of the sun through eclipse glasses or solar binoculars.

Chris Hartenstine, chief of public engagement at NASA’s Glenn Research Center in Cleveland, Ohio, said it will be clear when totality is reached.

“If you wear the eclipse glasses and look at the sun, you will see, even at the tiniest bit, the glow of the sun on the edge of that disk,” he said. “Once that’s completely off, give yourself a few more seconds and then you can take them off.”

Totality will last about three and a half to four minutes, depending on location, according to NASA.

Those viewing a partial solar eclipse must keep their special eclipse glasses on the entire time.

And the glasses are not enough for people who want to use tools like binoculars or a camera.

“Viewing any part of the bright sun through a camera lens, binoculars or telescope without a special solar filter attached over the front of the optic will cause immediate serious eye damage,” NASA warns.

How to ensure your glasses are safe

NASA does not endorse any particular brand of solar binoculars, but points to the American Astronomical Society’s list of safe options and recommends avoiding online marketplaces where third-party vendors might sell fake or poorly handled products. The association warned last week that fake and imitation glasses are ‘polluting the market’.

“The fewer hands that have to change places between the time they are produced and the time you hold them could increase your chances of not getting a bad or less desirable product,” Hartenstine said. .

Reusing eclipse viewing glasses is also an option if you are one of the millions who experienced the 2017 solar eclipse and held on to your glasses.

“The filters and the lenses themselves will last indefinitely,” Hartenstine said, although he added that you should make sure the lenses are not damaged, including from scratches, holes or creases.

‘If you’re not sure, obviously buy a new pair. But the expiration dates, just because they are printed on the glasses, do not apply to ISO standard sunscreen material,” Hartenstine said.

How to make and use a pinhole projector

If you can’t find good glasses, you can enjoy the solar eclipse without looking at it directly by making a pinhole projector.

The device works by letting sunlight in through a small hole, focusing it and projecting it onto a piece of paper, wall or other surface to create an image of the sun that you can safely look at.

To make a projector, cut a 1- to 2-inch square or rectangle from the center of a piece of plain white paper or white cardboard. Place a piece of aluminum foil over the cut out shape and then poke a small hole in the foil with a pin or thumbtack. Use a second piece of white paper or cardboard as a screen on which the projected image will appear.

To use your projector, place the paper screen on the floor, stand with the sun behind you and hold your device with the film facing up. Make sure you only view the projected image of the eclipse and do not look at the sun. Adjusting how far you hold the projector from the screen changes the size of the resulting image.

A colander or other household item with small holes in it can be used in the same way, and sturdier projectors can be made with cereal boxes.

Even simpler: find a shady tree and look at the ground beneath it; you’ll probably see crescent-shaped shadows.

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