The Eyes Have It. Viewing the 2017 Solar Eclipse Safely« Back
Published on July 26, 2017
Chief Health and Medical Officer at NASA - National Aeronautics and Space Administration
A solar eclipse occurs when the Moon blocks any part of the Sun. On Monday, August 21, 2017, a solar eclipse will be visible (weather permitting) across all of North America. With a fair swath being a total solar eclipse. The whole continent will experience a partial eclipse lasting 2 to 3 hours. Halfway through the event, anyone within a roughly 70-mile-wide path from Oregon to South Carolina(http://bit.ly/1xuYxSu) will experience a brief total eclipse, when the Moon completely blocks the Sun’s bright face for up to 2 minutes 40 seconds, turning day into night and making visible the otherwise hidden solar corona — the Sun’s outer atmosphere — one of nature’s most awesome sights. Bright stars and planets will become visible as well.
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.
As the moon moves in front of the sun, there comes a time when several bright points of light shine around the moon's edges. Known as Baily's Beads, these are light rays from the sun streaming through the valleys along the moon's horizon.Once the bright "diamond" disappears and there is no longer any direct sunlight coming toward you, you may look at the total eclipse safely. But you must still be vigilant to make sure you protect your eyes again before the end of totality. The entire total eclipse may take only a minute or two in some locations.
As the moon continues to move across the face of the sun, a crescent will begin to grow larger on the opposite side from where the Baily's Beads shone at the beginning. This crescent is the lower atmosphere of the sun, beginning to peek out from behind the moon and it is your signal to stop looking directly at the eclipse. Make sure you have safety glasses back on – or are otherwise watching the eclipse through a safe, indirect method -- before the first flash of sunlight appears around the edges of the moon.
Once your eyes are protected again, you may continue to watch the final stages of the eclipse as the end process mirrors the beginning: You will once again see a diamond ring and then the Baily's Beads, before the entire sun is once again visible.
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 five manufacturers have certified that their eclipse glasses and hand-held solar viewers meet the ISO 12312-2 international standard for such products: American Paper Optics, Baader Planetarium (AstroSolar Silver/Gold film only), Rainbow Symphony, Thousand Oaks Optical, and TSE 17.
- Always inspect your solar filter before use; if scratched or damaged, discard it. Read and follow any instructions printed on or packaged with the filter. Always supervise children using solar filters.
- Stand still and cover your eyes with your eclipse glasses or solar viewer before looking up at the bright Sun. After glancing at the Sun, turn away and remove your filter — do not remove it while looking at the Sun.
- Do not look at the uneclipsed or partially eclipsed Sun through an unfiltered camera, telescope, binoculars, or other optical device. Similarly, do not look at the Sun through a camera, a telescope, binoculars, or any other optical device while using your eclipse glasses or hand-held solar viewer — the concentrated solar rays will damage the filter and enter your eye(s), causing serious injury. Seek expert advice from an astronomer before using a solar filter with a camera, a telescope, binoculars, or any other optical device.
- If you are within the path of totality (http://bit.ly/1xuYxSu), remove your solar filter only when the Moon completely covers the Sun’s bright face and it suddenly gets quite dark. Experience totality, then, as soon as the bright Sun begins to reappear, replace your solar viewer to glance at the remaining partial phases.
A solar eclipse is one of nature’s grandest spectacles. By following these simple rules, you can safely enjoy the view and be rewarded with memories to last a lifetime.