A spectacular ‘ring of fire’ solar eclipse on Oct. 14 will be a sight worth viewing, but only with proper eye protection, according to Northeastern University experts.

“It’s dangerous to look at the eclipse without eye protection because of the ultraviolet light from the sun. Your natural defenses don’t work during an eclipse,” says Jonathan Blazek, an assistant professor of physics at Northeastern who has an expertise in astrophysics.

“It’s never safe to look directly at the sun, but normally it’s too bright to look at for long. Your pupils constrict to prevent too much light from getting in,” he says.

With even a partial eclipse of the sun, “there can still be dangerous UV light, but the sun is much less bright overall,” which affects the pupils’ ability to shrink and block waves of UV light, Blazek says.

And without proper protection, that can spell fast and permanent damage to the retina, the layer of cells lining the back wall inside the eye.

“The lenses in your eyes focus light onto the retina of your eyes. With a very powerful light source like the sun, all that light gets focused on one tiny spot and does a nice job of burning holes in your retina,” says Jacqueline McCleary, Northeastern assistant physics professor and observational cosmologist.

Think of a child using a magnifying glass and the sun’s rays to burn holes in a piece of paper, she says.

“The same will be true for a camera,” McCleary says. 

“The lenses of a camera focus all that bright sunlight onto a small spot on the film/sensor, and without a filter to attenuate some of the sunlight, the sensor will be damaged at least temporarily,” she says.

Even if the viewer is wearing special filters or eclipse glasses over their eyes, they can still damage their eyesight by looking at the sun through an unfiltered camera, binoculars or telescope, according to the American Astronomical Society.

“The concentrated solar rays could damage the filter and enter your eyes, causing serious injury,” the society says.

Where to see the ‘ring of fire’ eclipse

“Our friends in the Southwest, from Texas to California, will have the best view of the solar eclipse and also the best odds of clear skies,” McCleary says.

An eclipse map on NASA’s website shows that at the peak of the eclipse the sun will be blocked by 90% along a path stretching from Oregon, California, Nevada, Utah, Arizona, New Mexico and Texas, when it will show as a ‘ring of fire.’

The astronomical event Oct. 14 is officially known as an annular eclipse, when the moon passing in front of the sun leaves a circular fringe of light around its edges, which is what gives the eclipse its “ring of fire” nickname. 

In other areas of the Southwest, the sun will appear as a crescent during the eclipse’s peak. The NASA map shows that the Northeast will only see a 15-20% solar eclipse.

The space agency, which will be providing live coverage of the event, also has an interactive map that shows the main route of the eclipse, areas of the U.S. with different percentages of coverage, and a clock showing the path of the eclipse as it heads South.

Best protection: avoid counterfeits

While NASA doesn’t officially approve any particular brand of solar viewer, it says people viewing a partial or annular solar eclipse must look through solar viewing glasses, also known as eclipse glasses, or handheld solar viewers to avoid permanent eye injury.

Solar viewers are many thousands of times darker than even the darkest sunglasses, NASA says in an article devoted to eclipse viewing safety.

“Most filters or eclipse glasses are Mylar or a similar material which blocks most of the light,” McCleary says.

“If you want to take really fancy pictures of the sun, one can also buy special solar filters that let in only a tiny wavelength range,” she says. 

Before the eclipse, inspect eclipse glasses and handheld viewers and toss them if they are torn, scratched or otherwise damaged, NASA officials say. 

They ask parents and guardians to supervise children using the devices and advise people purchasing solar viewers to check the American Astronomical Society’s list of suppliers to guard against devices that falsely claim to meet the ISO 12312-2 international safety standard. 

A total eclipse occurs in April

No part of an eclipse is safe to view with the naked eye except during the moments of a total eclipse when the moon completely blocks the bright surface of the sun.

During the annular or ring of fire eclipse, the moon is further away from the Earth than normal and “isn’t quite big enough to block the sun” at any point, Blazek says.

He says the next total eclipse will occur in April, when “the moon is a bit closer to the Earth and is thus able to block the entire sun.”

And in good news for New Englanders and others, “it will be visible in the Eastern part of the U.S. rather than the Western half,” Blazek says.

Cynthia McCormick Hibbert is a Northeastern Global News reporter. Email her at c.hibbert@northeastern.edu or contact her on Twitter @HibbertCynthia .