Looking directly at the sun is unsafe. Even during the upcoming solar eclipse, the only safe way to look directly at the eclipsed sun is through special-purpose solar filters, such as “eclipse glasses” or other equipment that is outfitted for safely viewing the Sun. Regular sunglasses, even very dark ones, are not safe for looking at the Sun – they simply let in too much dangerous sunlight.
To make sure you are buying solar safe equipment you can go to the American Astronomical Society’s Reputable Vendors of Solar Filters & Viewers page for a list of manufacturers and authorized dealers of eclipse glasses and handheld solar viewers verified to be compliant with the ISO 12312-2 international safety standard for such products.
NASA has released an advisory on how to safely view the solar eclipse. Here are specific recommendations as provided by NASA:
– 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 looking 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. Note that solar filters must be attached to the front of any telescope, binoculars, camera lens, or other optics.
– If you are within the path of totality, you can 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 look at the remaining partial phases.
– Outside the path of totality, you must always use a safe solar filter to view the sun directly.
– If your eclipse glasses or viewers are compliant with the ISO 12312-2 safety standard, you may look at the uneclipsed or partially eclipsed Sun through them for as long as you wish. Furthermore, if the filters aren’t scratched, punctured, or torn, you may reuse them indefinitely. Some glasses/viewers are printed with warnings stating that you shouldn’t look through them for more than 3 minutes at a time and that you should discard them if they are more than 3 years old. Such warnings are outdated and do not apply to eclipse viewers compliant with the ISO 12312-2 standard adopted in 2015.
– An alternative method for safe viewing of the partially eclipsed sun is pinhole projection. For example, cross the outstretched, slightly open fingers of one hand over the outstretched, slightly open fingers of the other, creating a waffle pattern. With your back to the sun, look at your hands’ shadow on the ground. The little spaces between your fingers will project a grid of small images on the ground, showing the sun as a crescent during the partial phases of the eclipse. Or just look at the shadow of a leafy tree during the partial eclipse; you’ll see the ground dappled with crescent Suns projected by the tiny spaces between the leaves.
NASA also provides much more information on the Great American Solar Eclipse on its 2017 eclipse website.
The Astronomy Technology Today editorial staff would like to take this opportunity to remind you of the availability of our Solar eclipse equipment guide – The Definitive Equipment Guide to the 2017 Solar Eclipse. Our goal with the 40 page publication is to provide an easy-to-consume introduction to the technological options for viewing and imaging the Great Solar Eclipse. We cover the gamut of options available including building your own solar viewer, solar glasses, smart phones, DSLR cameras, using astronomy telescopes, solar telescopes, using binoculars, solar filters (including a DYI filter option), CCD astro cameras, astro video cameras, webcams and much more. You can view the guide on our website here – its free and there is no requirement to sign up to read the guide.