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People in the United States will be treated to an awesome show in the sky Aug. 21, 2017: a solar eclipse.
A solar eclipse occurs when the moon passes between Earth and the sun, blocking the sun from view. The U.S. hasn’t seen a total solar eclipse since 1979, and it’s the first time one has moved from coast to coast in nearly a century. We won’t see another one until 2024.
Those of us in the Washington metropolitan area can expect to see about 80 percent coverage of the sun. The eclipse will be visible in Washington D.C., from 1:17 pm to 4:01 pm EDT, with a maximum eclipse at 2:42 pm EDT. Even though we’re not in the path of totality, in which the sun is completely covered by the moon, it will still be a sight you’ll want to see. However, before you look up, take some safety precautions to protect your eyes. Even the small amount of sunlight we’ll get on this day can damage the sensitive tissues of the eyes.
1. Do not look at the sun with the naked eye
On a normal day, looking directly at the sun is uncomfortable, causing us to blink and look away. But as the moon blocks more and more of the sun’s light during a solar eclipse, your pupils become larger to let in more light. This disengages the normally protective pupillary response to keep out harmful unnecessary light rays, allowing the sun’s ultraviolet rays to enter your eyes.
Your lens acts like a magnifying glass by focusing light onto the retina. The retina is the layer of cells at the back of the eyeballs that are sensitive to light and trigger nerve impulses to the brain, forming a visual image. When sunlight enters the eye, it can burn a hole in the retina, much like using a magnifying glass to burn holes in leaves or paper.
Eye damage caused by looking directly at the sun is known as solar retinopathy. Because the retinas lack pain receptors, you can permanently damage your vision without even feeling it. Once the cells are dead, the damage can’t be undone. And it only takes a few seconds.
The degree of damage can vary. Symptoms can include:
- A blind spot in your central vision
- Blurred vision
- Difficulty discerning shape and detail
- Discomfort with bright light
The only time you can look at the sun with your naked eye is if you’re in the path of totality. And even then, you can only do it during the short time the sun is completely covered—around two minutes, depending on where you are.
2. Wear eclipse glasses that meet international standards
Put away your sunglasses. They won’t protect your eyes from looking directly at the sun—even during an eclipse. Looking through multiple pairs of sunglasses won’t work either.
You have a couple protective eyewear options. The first is No. 14 welder’s goggles, the only goggles dark enough for safe solar viewing.
Your other option is eclipse glasses that contain special-purpose solar filters that meet international standard ISO 12312-2 for safe viewing. These glasses filter out the majority of natural light but will allow you to see the eclipse.
Inspect your eclipse glasses before using them on the big day. You shouldn’t be able to see anything through these glasses except the sun. If you can, they won’t protect you. Also, check for scratches or other damage.
Eclipse glasses are in high demand right now, and unfortunately, there have been reports of companies selling products labeled as if they conform to international safety standards, but they actually do not. Check out the American Astronomical Society’s list of companies whose products have been verified by a testing laboratory to meet these standards.
Finding eclipse glasses may take some work. Many retail stores have sold out. The good news is that all sorts of organizations are handing out free eclipse glasses, including the Smithsonian’s National Air and Space Museum. You also can check out your local library. Thousands of libraries across the country are giving away the glasses. Find a map of participating libraries.
3. Make a pinhole camera
You don’t need to look straight at the sun to watch a solar eclipse. You also can watch it indirectly with a handmade pinhole camera.
NASA’s Jet Propulsion Laboratory recommends this easy process:
- 2 pieces of white card stock (white paper plates work)
- Aluminum foil
- Pin or paper clip
- Cut a square out of the middle of one of the pieces of cardstock.
- Tape a piece of aluminum foil over the square.
- Poke a hole in the foil using the pin or paper clip.
- Place your second piece of cardstock on the ground.
- Stand with the sun behind you and hold the cardstock with the aluminum foil hole above your shoulder, allowing the sun to shine through the hole and onto the cardstock on the ground. The eclipse will be projected onto the cardstock on the ground.
4. Watch the eclipse on a monitor
If you can’t get your hands on protective eyewear or don’t want to make a pinhole viewer, you can watch the solar eclipse on TV, a computer or your smartphone. It may not be the same as seeing it firsthand, but your eyes will be protected.
The Smithsonian’s Air and Space Museum is hosting a viewing of the eclipse at the the Smithsonian’s National Zoo’s Pachyderm Plaza from 1 to 4 p.m. and offers a view of the solar eclipse through a safe solar telescope.
5. Use a solar filter on your camera, telescope or binoculars
A solar eclipse can make for a stunning photo but will require a few extra safety precautions. Just like you need to wear eclipse glasses, you’ll also need to attach a solar filter to your camera (yes, this includes your smartphone), telescope or binoculars to protect the device from damage as well.
Don’t look at the eclipse through an unfiltered camera, telescope or binoculars—even if you’re wearing your eclipse glasses. The concentrated solar rays could damage the glasses’ filter and injure your eyes.
Bonus safety tips
While the solar eclipse poses the greatest danger to your eyes, there are a few other things to keep in mind:
- Prepare for a drop in temperature: In the path of totality, temperatures likely will drop 10 degrees or more. Even in D.C., where the moon will cover the sun only partially, we’ll feel a slight chill. Grab a jacket or blanket before you head out, just in case.
- Drive safely: If you want to see the eclipse, pull over. Don’t watch and drive. Even if you’re not watching the eclipse, expect other drivers to be doing so. Pay extra attention to the road and those around you.
- Wear sunscreen: Even though the sky will turn dark during the eclipse, the sun’s rays will still be hitting your skin. Don’t forget to apply some sunscreen.
By following these simple tips, you can stay safe and comfortable during this awe-inspiring event. Enjoy the show!