DENVER – The most anticipated astronomical event in decades is now just a few weeks away.
On Aug. 21, 2017, the best total solar eclipse in 40 years will make its way across the United States, providing skywatchers a rare chance to see the moon pass directly in front of the sun.
Most of the country will see at least 75 percent of the sun obscured. A 70-mile wide path from Oregon to South Carolina will see a total eclipse of the sun.
Before making plans to watch the eclipse, it’s important to plan for safety. Staring directly at the sun for any amount of time will damage one’s eyes, so using protective equipment is crucial.
Whether you’re making a trip of it or staying at home, here are some tips to make sure you enjoy the eclipse without damaging your eyes.
Specially-made glasses/solar viewer
One of the easiest ways to safely watch the eclipse is to use a handheld solar viewer or glasses that are specially made for that purpose. Several companies make such glasses and viewers and you can buy many of them at Amazon.com or other major retailers. The American Astronomical Society recommends products made by Rainbow Symphony, American Paper Optics or Thousand Oaks Optical.
Just make sure whatever glasses/viewers you use are ISO-certified, so you know they meet international standards for safety. Sunglasses are NOT dark enough and you WILL damage your eyes by staring at the sun with only sunglasses on. Eclipse glasses are thousands of times darker than sunglasses.
If you’re planning to take photos of the eclipse or view it through a telescope or binoculars, you’ll need a solar filter (note that a polarizing filter is not good enough). This will protect both your eyes and the lenses in your device. Make sure you follow the directions included with your filter and never use a filter that’s been damaged or scratched.
You don’t have to look directly at the sun to watch the eclipse. There are several projection methods that will make it possible for several people to safely view the eclipse at once. The pinhole method involves poking a small hole in a piece of paper or card stock and then placing another piece of paper or card a few inches away at a parallel angle. The image of the sun should appear on the unaltered piece of paper.
You can achieve a similar effect using binoculars or a telescope to project the sun onto a sheet of paper or card stock. Just make sure nobody looks through the telescope/binoculars at the sun.
Can I use my smartphone?
According to NASA, there’s some debate about whether the bright rays of the sun will damage a smartphone camera. Most photographers agree that brief exposure to the sun should be fine, since smartphone cameras are generally very small and automatically adjust the exposure and other settings to limit how much sunlight will get in.
Just be aware that phone cameras are not made for taking pictures of objects in the sky and therefore won’t get very good pictures. The sun will be very small and probably blurry, so if you want to take photos, you should use a larger, professional-style camera.
NASA has more tips for using a phone camera here.
What about a welding helmet?
A welding helmet will work for safely viewing the eclipse as long as you can ensure the helmet is fitted with a filter that is dark enough. Filters made for gas welding or cutting are not dark enough to protect your eyes. According to the AAS, filters with shade numbers 12 to 14 should be dark enough, though some might find a number 12 filter to be too bright.
CU Boulder’s Fiske Auditorium has a wealth of additional information on the eclipse on its website here.