Getting Ready for Solar Eclipse 2017, Safety Review
The countdown to The Great American Eclipse continues. At about 11:37 AM on August 21, 2017 Sioux Falls will experience a near total eclipse of the sun.
Our friends just to the south in Nebraska will get to enjoy the full eclipse, but here in the city we will experience about 90% totality. That means it's still going to still get pretty dark, and it's still going to be a super exciting experience.
We won't have another total solar eclipse in the Continental United States until April 8, 2024.
As exciting as this total eclipse is, there are some safety measures that need to be taken when viewing an eclipse. According to NASA:
Looking directly at the sun is unsafe except during the brief total phase of a solar eclipse (“totality”), when the moon entirely blocks the sun’s bright face, which will happen only within the narrow path of totality
The problem is that looking at the sun damages rods and cones in the retina that are very sensitive to light. Even a small portion of the suns surface can hurt your eyes.
It takes a few seconds for this to happen, but afterwards you will see a spot as big as the solar surface you glimpsed when you look away from the sun at some other scenery. Depending on how long you gazed at the sun and how badly the retinal cells were damaged, this spot will either fade away in time or remain permanent. You should never assume that you can look away quickly enough to avoid eye damage because every person is different in terms of their retinal sensitivity, and you do not want to risk being the one who damages their eyes just to try to look at the sun.
So what does all that mean? First, you cannot watch the eclipse with the naked eye. We can't walk out during lunch on August 21 and stare skyward. We can't just wear our sunglasses either.
The only safe way to look directly at the uneclipsed or partially eclipsed sun is through special-purpose solar filters, such as “eclipse glasses” or hand-held solar viewers. Homemade filters or ordinary sunglasses, even very dark ones, are not safe for looking at the sun. To date four manufacturers have certified that their eclipse glasses and handheld solar viewers meet the ISO 12312-2 international standard for such products: Rainbow Symphony, American Paper Optics, Thousand Oaks Optical, and TSE 17.
So, wear eclipse glasses if you want to look at the sun during the event. A person also can't look directly at the eclipse through an unfiltered camera lens, telescope or other unfiltered device.
If you don't want to wait to watch video of the sun and moon's celestial dance later in the day, you can view the eclipse with the pinhole projection method. All it takes is a couple peices of stiff white paper or cardboard.
Punch a small clean pinhole in one piece of cardboard and let the sunlight fall through that hole onto the second piece of cardboard, which serves as a screen, held below it. An inverted image of the Sun is formed. To make the image larger, move the screen farther from the pinhole. To make the image brighter, move the screen closer to the pinhole. Do not make the pinhole wide or you will only have a shaft of sunlight rather than an image of the crescent Sun. Remember, this instrument is used with your back to the Sun. The sunlight passes over your shoulder, through the pinhole, and forms an image on the cardboard screen beneath it. Do not look through the pinhole at the Sun. -Mr Eclipse
Here's a little more complicated, but still easy version:
Even if you just want to experience the darkness and watch video later, this is going to be a spectacular event.