How to safely view a solar eclipse.
How to Safely View a Solar Eclipse
Credit: Marco de Swart/ANP/AFP via Getty Images
Use these tips and techniques to get the best live view of the eclipse—without damaging your eyes!
Never view the Sun with the naked eye or by looking through unfiltered optical devices such as binoculars or telescopes!
This is critical! Why? You may have taken a magnifying glass out into the Sun and burned leaves with it. If so, you’ll remember that when sunlight is focused onto a small spot with a lens, it can start a fire. Your eye also has a lens, and if you look at the Sun without proper protection, your eye’s lens will focus sunlight onto a very small spot on the retina on the back of your eye. This literally burns your eye, causing permanent eye damage or blindness. In addition, since there are no pain sensors in your retina, you won’t even know it’s happening!
It is never safe to look at an annular eclipse without eye protection, but during a total solar eclipse, there are a few short moments when it’s safe to look directly at the Sun. This is the ONLY time: when the moon completely blocks the face of the Sun. Called totality, it lasts from a few seconds to a few minutes. The instant the moon begins to move off the Sun’s face, you must go back to using safe viewing techniques.
Solar Viewing Glasses
Solar viewing glasses—also called eclipse glasses—are an easy, affordable way to safely look at a solar eclipse. Without these special glasses, the Sun can permanently damage your eyes or cause blindness. We recommend that you DO NOT purchase eclipse glasses on Amazon or other third-party sites, as unscrupulous people have been selling glasses that do not meet the international standard for filters that allow for direct viewing of the Sun (even though they are sometimes marked as such). These counterfeit glasses could damage your eyes.
You can purchase solar viewing glasses online at the Exploratorium store.
Other vendors approved by the American Astronomical Society include:
How to Make a Pinhole Projector
There are safe ways to view the sun. The simplest requires only a long box (at least six feet long), a piece of aluminum foil, a pin, and a sheet of white paper.
The length of the box is important: the longer the box, the bigger your image of the sun will be. To estimate how big the image will be, multiply the length of the box by 0.01. For example, if your box is six feet (72 inches) long, your solar image will be 72 x 0.01 = 0.72 inches in diameter, or about ¾ inch.
1. Find or make a long box or tube. If you can’t find a long tube, you can tape together two or more shorter ones. (Two triangular shipping tubes, taped together, make a good solar viewer.) Cut out the cardboard at one end of each tube and tape those ends together with duct tape, so that light can travel the length of the tube.
2. Cut a one-inch hole in the center of one end of the box. Tape a piece of foil over the hole, then poke a small hole in the foil with a pin.
3. At the other end of the tube, cut a good-sized viewing hole in the side of the box. Put a piece of white paper at the end of the box, right inside the viewing hole. This is the screen where your projected Sun will appear.
To use your viewer, point the pinhole end of the box right at the Sun. To aim it, move it around until you see a round spot of light on the paper at the other end—that’s your pinhole image of the Sun! If you have trouble aiming your viewer, look at the shadow of the box on the ground. Move it until the shadow is as small as possible—that is, until it looks like the end of the box and the sides are not casting a shadow. Do not look through the pinhole at the Sun! Look only at the image on the paper.
Quick and Easy Viewing Techniques
Here are some ways to watch the Sun that are even easier.
Use two pieces of cardboard. In one, cut a one-inch hole, then tape a piece of foil over the hole. Now make a pinhole in the middle of the foil. Use the other piece of cardboard (which should be white for best viewing) as a screen. With the Sun behind you, hold the pinhole cardboard as far from your screen as you can. The farther the pinhole is from the screen, the bigger your image will be.
Use your hands. Hold both hands with your fingers overlapping at right angles. The holes between your fingers make pinholes, forming images of the Sun on the ground.
Use a tree. If you have shade trees in your location, try looking at the images of the Sun coming through the holes formed by the leaves. Use a piece of white cardboard to capture the images for a great viewing session!
Use a colander. A colander, with its many holes, will give you fantastic, multiple images of the sun. Simply hold it about 20" above the ground. The images will look even better if you cast them onto a white piece of paper or sheet.
Pinhole images are pretty dim and small. You can magnify the Sun’s image by using a pair of binoculars. You MUST NOT look through the binoculars!
1. Firmly attach the binoculars to a tripod, eyepieces facing down. You can do this with duct tape—what else?
2. Make a Sun shield from a piece of cardboard. Cut a hole for one of the lenses. (You don’t need them both.) Then tape the shield to the front of the binoculars with the lens sticking through the hole. Use duct tape to seal any holes that leak light past the cardboard shield.
3. Point the binoculars toward the Sun while holding a piece of white cardboard about one foot beyond the binoculars.
4. It will take a little effort to find the Sun. Once you do, you can focus the binoculars to bring the Sun to a sharp image.
DO NOT put your hand or anything flammable near the eyepiece. The concentrated sunlight exiting there can cause a nasty burn or set something ablaze!
Now you can watch a beautiful, bright, magnified image of the sun as the eclipse proceeds. You will have to adjust the tripod periodically to account for the Earth's rotation. A warning: give your binoculars a cooling break now and then. The eyepiece may become overheated and the lens elements may separate if you leave it pointed at the Sun for too long.
If you can't keep yourself from looking directly at the Sun, be absolutely sure that you have the correct filter--a professionally designed white light filter that blocks 99.999 percent of the sunlight. Just because a filter makes the Sun look dim does not mean that it’s blocking enough of the dangerous amount of sunlight that can permanently damage your eyes.
Do NOT use sunglasses, polaroid filters, smoked glass, exposed color film, X-ray film, or photographic neutral-density filters.
Do NOT use this type of telescope filter:
Make sure that the supplier of your eclipse filter is reputable and reliable—a few are listed below. “Eclipse glasses” are inexpensive filters in cardboard frames made especially for eclipse viewing. You can purchase them online, and usually at science museum stores in areas where an eclipse is visible. You can also look at the Sun with a number 14 welder’s glass, available at welding supply stores.
If you want to use a filter on a telescope, use only the filter supplied by the manufacturer or by a manufacturer who makes the filter specifically for the instrument you are using. However, if the manufacturer’s filter is the type that screws onto the eyepiece, DO NOT USE IT! The manufacturers of some inexpensive telescopes supply a welder's glass filter that screws onto the eyepiece. It may heat up and crack as you are looking through the telescope. A proper solar filter always goes on the front end of the telescope, blocking the sunlight before it enters the optical system.
By following the instructions above and using a modicum of good sense, you will be able to enjoy solar eclipse after solar eclipse.
Vendors approved by the American Astronomical Society include:
- Thousand Oaks Optical (for camera filters and sheets of filter material)