Like millions of other people, Wanda Diaz Merced plans to observe the August 21 total solar eclipse, when the moon’s shadow will sweep across the sun and, for a few brief moments, coat parts of the United States in darkness. But she won’t see it. She’ll hear it.

Diaz Merced, an astrophysicist, is blind, with just 3 percent of peripheral vision in her right eye, and none in her left. She has been working with a team at Harvard University to develop a program that will convert sunlight into sound, allowing her to hear the solar eclipse. The sound will be generated in real time, changing as the dark silhouette of the moon appears over the face of the bright sun, blocking its light. Diaz Merced will listen in real time, too—with her students at the Athlone School for the Blind in Cape Town, South Africa, where she teaches astronomy.

“It’s an experience of a lifetime, and they deserve the opportunity,” Diaz Merced said.

To capture the auditory version of this astronomical event, the team turned to a piece of technology measuring only a couple inches long: the Arduino, a cheap microcomputer popular with tech-savvy, DIY hobbyists. With a few attachments, Arduinos can be used to create all kinds of electronic devices that interact with the physical world, from the useful, like finger scanners that unlock garage doors, to the silly, like motion-detecting squirt guns. Diaz Merced’s collaborators equipped an Arduino with a light-detecting sensor and speaker, and programmed it to convert light into a clicking noise. The pace of the clicks varies with the intensity of the sunlight hitting the sensor, speeding up as it strengthens and slowing down as it dims. In the moments of totality, when the sun’s outer atmosphere appears as a thin ring around the shadow of the moon, the clicks will be a second or more apart.

Allyson Bieryla, an astronomy lab and telescope manager at Harvard, will operate the Arduino from Jackson Hole, Wyoming, inside the path of totality. She will stream the audio on a website online, which Diaz Merced will open on her computer in Cape Town.

So far, Bieryla says, “the real challenge has been trying to find a light sensor that’s sensitive enough to get the variation in the eclipse.” In totality, the sun will appear about as bright as a full moon at midnight. The team has tested the Arduino at night, under the moonlight, to make sure it can pick up the faint luminosity.

Diaz Merced, a postdoctoral fellow at the Office of Astronomy for Development in South Africa, was diagnosed with diabetes as a child. In her early 20s, when she was studying physics at the University of Puerto Rico, she was diagnosed with diabetic retinopathy, a complication of the disease that destroys blood vessels in the retina. Her vision began to deteriorate, and a failed laser surgery damaged her retinas further, she said. By her late 20s, she was almost completely blind. She recalls watching a partial solar eclipse in 1998 in Puerto Rico, when she still had some sight.

“I was able to experience the wonderfulness—of the sun being dark, of having a black ball in the sky,” she said. “That is why it is important to use the sound in order to bring an experience that will bring that same feeling to people who do not see or are not visually oriented.”

While Diaz Merced experiences the eclipse from a classroom in Cape Town, Tim Doucette will observe the event at a campground in Nebraska, smack-dab in the path of totality. Doucette is a computer programmer by day and an amateur astronomer by night. He runs a small observatory, Deep Sky Eye Observatory, near his home in Nova Scotia in a sparsely populated area known for low light pollution and star-studded night skies.

Doucette is legally blind, and has about 10 percent of his eyesight. He had cataracts as a baby, a condition that clouds the lenses of the eye. To treat the disease, doctors surgically removed the lenses, leaving Doucette without the capacity to filter out certain wavelengths. His eyes are sensitive to ultraviolet and infrared light, and he wears sunglasses during the day to protect his retinas. Without shades, Doucette said he can’t keep his eye open in the brightness of day.  But at night, his sensitivity becomes an advantage. With the help of a telescope, Doucette can see the near-infrared light coming from stars and other objects in the sky better than most people.

“My whole life, I’ve always been asking people for help, saying, ‘hey, what do you see?’” Doucette said. “When I stargaze with people, the tables are reversed.”

Doucette sees best at night, safe from the glare of the sun. He uses starlight to guide him during the short walk from his observatory to his home. “When I’m walking down the road, especially during the summer months, the Milky Way is just this incredible painting going from north to south,” he said. “It’s millions and millions of points of light. It’s like a tapestry of diamonds against a velvety background.”

Doucette, armed with his camera equipment, will observe the eclipse with dozens of members of the Royal Astronomical Society of Canada’s Halifax Center, an association of amateur and professional astronomers. He has only witnessed partial solar eclipses in the past. “It should be quite interesting to see what the effect is because of my sensitivity,” he said. During totality, when day becomes night, some objects in the sky may become visible, thanks to his sensitivity to their light.

Doucette will wear eclipse sunglasses over his regular pair. Eclipse glasses protect the eyes from sunlight so viewers can look directly at it without hurting their eyes, and they can be bought online for a few dollars. Doucette urged eclipse viewers to use them, citing stories he’d heard of people looking at the sun during an eclipse and waking up blind the next morning, their retinas burned. The shades are necessary before and after totality, when the sun is only partially eclipsed and a thin crescent shines with typical intensity.

“Once the eclipse is in totality for about two and a half minutes, I’m told that it’s safe to take the glasses off, but I’m not willing to risk it,” Doucette said. “I’ll still keep my sunglasses on either way.”