Friday, August 4, 2017

Public Service Announcement: Total Solar Eclipse August 2017

On Saturday March 7, 1970 there was a total solar eclipse visible from New Jersey, which is where I lived at the time (and still do today).

My mother made us stay in the house, with all of the shades drawn down, so that we would not go blind.

As neither me nor any of my siblings are blind it must have worked!

This month there will be another total solar eclipse, visible in all or part, across the entire continental United States. And I'm sure we'll see all manner of pseudoscientific silliness of the kind that so worried my mom.

It is true that viewing the sun can lead to blindness. Yet it is also true that one can view all of the phases of the upcoming eclipse in perfect safety. The key is knowing how to view the eclipse and having suitable eye protection when doing so.

In the image below, the moon is completely covering the sun's disk. At this point, which will last just over two minutes in most places, it is perfectly safe to view the sun with the naked eye. But this is the only time for which it is safe to do so.

Solar Corona

But as soon as the sun peaks out from behind the moon, as in the image below, it is no longer safe to look at the sun without adequate eye protection.

If any part of the sun's disk is visible you need eye protection.

Diamond Ring

While it may seem that the sun is dim enough to view directly, infrared and ultraviolet radiation are slowly burning your retina at this point. As there are no pain receptors in your retina you'll have no idea this is happening.

And your vision will be permanently damaged.

Eclipse glasses which are compliant with the ISO 12312-2 safety standard are inexpensive and widely available (click the link to find reputable sources). If you plan to do any eclipse viewing at all now is the time to get a pair of eclipse glasses. This link, to B&H Photo, has a five pack of glasses for $7.99. That's $1.60 each and is representative of the cost.

Enjoy the show. Be safe and smart while doing so.

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