In the style of an airline safety announcement, NASA describes how to safely view the 2017 total solar eclipse that will cross the continental United States on Aug. 21.
The NASA "airline attendants" caution against looking directly at the sun; instead, eclipse enthusiasts can use eclipse glasses, construct pinhole viewers, build pinhole projectors or even shape their fingers to project a view of the eclipse. It's also important to avoid looking at the sun with a telescope or camera viewfinder without a solar filter, and to avoid looking through a telescope with eclipse glasses on, as the concentrated light could hurt the glasses. [Total Solar Eclipse 2017: When, Where and How to See It (Safely)]
Viewers can glimpse the eclipse directly during totality — when the sun is completely covered by the moon and a view through eclipse glasses is dark. The attendants warn viewers to be sure to stop looking before the first glint of sunlight appears again. You can research whether a total solar eclipse will be visible in your area, where you can travel to see it and how long it will last.