Experts give tips for safe viewing of April’s total solar eclipse
NICOLE Bajic, an ophthalmologist at the Cleveland Clinic Cole Eye Institute in Ohio, who is among the eye doctors, specialists and eclipse experts advising enthusiastic viewers across the country on how they can make April’s total solar eclipse as safe – and as fun – as possible.
During a total solar eclipse, the moon appears to completely cover the sun, casting its shadow along its trajectory above the Earth. This year’s eclipse will be the second of its kind in the 21st century to touch the contiguous U.S. There won’t be another one until 2044.
Experts say anyone in northern Mexico, parts of Canada, or one of 15 U.S. states from which the eclipse can be seen on April 8 should also prepare.
Even though most people in the U.S. will be able to see at least a partial solar eclipse that day, only those in the 115-mile-wide (185.07-kilometer-wide) path of totality – right under the moon’s shadow – will be able to take their glasses off for approximately four minutes briefly.
For specialists, safety is at the top of their minds. But understanding how the eyes absorb light and perceive color can help viewers enjoy a short-lived, possibly once-in-a-lifetime, stargazing event.
The eye will notice light dimming five to 10 minutes before the eclipse’s totality. Two minutes before the main event, red colors will fade and contrast with greens and blues in a biological phenomenon called the Purkinje effect.
Normally, as day transitions into night, the eyes adjust to the dark as rod cells become more active than cone cells. This period, called dark adaptation, can take anywhere between 30 minutes and two hours.
So the retina takes a while to adjust to the quick change. This part of the eye has two types of photosensitive cells that convert light into signals sent to the brain that allow humans to see the world. Cones are the receptors responsible for colorful vision in the daytime. Rods are the receptors that work in low-light conditions and allow for nighttime vision.
Those who want to look at the sun as the moon partially or completely obscures it should secure a pair of safe solar glasses in advance. But eclipse viewers should also keep other things in mind, especially if they have eye conditions.
Those who prefer not to venture a peek can get creative with the easy pinhole projection method, which works best during a partial eclipse or when a total solar eclipse has yet to reach totality.
When sunlight passes through small holes –punched in an index card or cardboard box, on a pasta colander or straw hat, or through outstretched fingers on crossed hands – and lands on a flat surface, it projects the sun’s crescent shape in a grid pattern. Spaces between tree leaves can also create pinhole projections.