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On April 8, a stunning total solar eclipse will be visible to millions of people in Mexico, the United States and Canada.
Astronomers are encouraging everyone on the trail to enjoy this rare sight for the 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 heavenly event.
A total solar eclipse occurs when the moon passes between the Earth and the sun, completely blocking the face of the sun.
Those within the path of totality, or locations where the moon’s shadow will completely cover the sun, will see a total solar eclipse. People outside the path of totality will still be able to see a partial solar eclipse, in which the moon blocks only part of the sun’s face.
If your location only offers a view of the partial eclipse, some of the sun’s powerful light will always be visible. 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 solar eclipse
The only time it’s safe to look at the sun without eye protection is during the “totality” of a total solar eclipse, or the brief moments when the moon completely blocks the sun’s light, according to NASA.
Staring directly at the sun can lead to blindness or impaired vision. During the 2017 total solar eclipse, a young woman was diagnosed with solar retinopathy, damage to the retina due to exposure to solar radiation, in both eyes after viewing the eclipse with what doctors thought were eclipse glasses that were not on the safety standard met.
There is no treatment for solar retinopathy. It may improve or worsen, but it is a permanent condition.
Use of eclipse glasses and solar binoculars
To view the solar eclipse, you will need to wear certified eclipse glasses or use a portable solar viewer. In addition, you can observe the sun with a telescope, binoculars or camera with a special solar filter on the front, which works in the same way as eclipse glasses.
“You need certified solar eclipse glasses that meet ISO 12312-2. There are plenty of secure vendors online,” said Alex Lockwood, chief of strategic content and integration for the Science Mission Directorate at NASA Headquarters. “We cannot emphasize enough how important it is to obtain safe, certified solar eclipse glasses to witness this annular event.”
Sunglasses do not take the place of eclipse glasses or solar binoculars, 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 virtually all visible, infrared and ultraviolet light, according to The Planetary Society. Sunglasses do not block infrared radiation.
For safe manufacturers and resellers of eclipse glasses and filters for optical devices, including cameras and smartphones, check out the list compiled by the American Astronomical Society.
Put on your eclipse glasses before looking up and remember to turn away from the sun before taking them off. Always supervise children wearing eclipse glasses to ensure they do not remove them while looking at the sun.
If you normally wear glasses, keep them on and place eclipse glasses over them or hold a portable viewer in front of them, according to the American Astronomical Society.
Don’t look at the sun through an unfiltered optical device — camera lens, telescope, binoculars — while wearing eclipse glasses or using handheld solar binoculars, according to NASA. The sun’s rays can still burn through the filter of glasses or binoculars, given how concentrated they can be through an optical device, and can cause serious eye damage.
It is also possible to use welding filters to view the solar eclipse safely, as the international safety standard is partly derived from using such filters to view the sun.
Welding filters made of tempered glass or metal-coated polycarbonate and with a color number of 12 or higher provide safe viewing, but many find color 13 or 14 best and comparable to wearing eclipse glasses, according to the American Astronomical Society. Just know that the sun will appear green instead of yellowish orange or white. These filters are usually not available in stores, but may be available online.
Auto-darkening or adjustable welding helmets are not recommended because they may not darken quickly enough to see the sun.
Save your glasses
As long as the eclipse glasses or solar binoculars you use meet the ISO 12312-2 safety standard and are not cracked, scratched or damaged in any way, they will not “expire” and can be used indefinitely. There is also no limit to how long you can look at the sun while wearing them.
Some glasses and binoculars carry outdated warnings about using the glasses for more than three minutes at a time or recommend throwing them away after more than three years, but these don’t apply to ISO 12312-2-certified, according to the American Astronomical Society viewers. .
Preserve your eclipse glasses and binoculars for future eclipses by storing them at room temperature in an envelope or in the original packaging to prevent scratches.
Never use water, glass cleaner, baby wipes or other wet wipes to clean the eclipse glasses; the moisture can cause the cardboard frames to separate from the lenses. Instead, gently wipe the lenses with a tissue or cloth.
Indirect view of the solar eclipse
If you don’t have certified glasses on hand, eclipses can also be viewed indirectly with a pinhole projector, such as a hole in an index card. These work if you stand with your back to the sun and hold the card up. The pinhole projects an image of the crescent-shaped or annular sun onto the ground or other surfaces.
But never look at the sun and look directly at it through the hole.
Other pinhole projectors you may already have on hand include colanders, straw hats, or anything else with small holes in them. Or you can simply hold your hands up, spread your fingers and cross them over each other to create a waffle pattern. The small space between them reflects the Sun’s crescent during a partial solar eclipse or a ring during the annular solar eclipse.
Standing by a leafy tree? The small spaces between the leaves will stain patterns of the eclipse phase on the ground.
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