How Safe are Eclipse Glasses ?

How Safe are "Eclipse Glasses"?

Just how safe are these Eclipse Glasses? Ever since I learned that the sun actually burns holes in the retina of your eye, I've been paranoid of using any device that will allow "safe" viewing of the sun.

From what I've been told, everyone has at least 3-6 "holes" in the retina, from looking at the sun as a baby (I guess it takes them 3-6 times to figure out "looking at the sun = BAD").

http://eclipseshades.com/

Safe Solar Glasses for Australian Eclipse 2012. Absolutely safe for direct solar viewing of solar eclipses sun spots and other solar phenomenon. All of Our Eclipse Glasses Solar Viewing Materials are Optical Density 5 or Greater and are "CE" certified which meets the transmission requirements of scale 12-16 of EN 169/1992. Certified by BSI #0086 Notified Body HP2 4SQ. Meets the 2012 Transmission Requirements of EN 1836:2005 & AS/NZS 1338.1:1992 for Eclipse filters. Lenses are made of our exclusive scratch resistant optical density 5, "Black Polymer" material. Eclipse Shades filter out 100% of harmful ultra-violet, 100% of harmful infrared, and 99.999% of intense visible light.

I've never personally used one, but if the filter does not just make the sun appear dim but also blocks infrared or ultraviolet radiation, then you should be good to go. I know that I've been to a few science museums, including NASA, that sold these things at the gift store, so based on that I'm going to assume that eclipse glasses can work and be safe.

I found an article that is somewhat relevant: Community Eye Health. Here's a snip from the article.

At another eye hospital, workshops had been set up to educate village volunteers, who would then take the message back to their respective regions. The lectures were designed to inform people on what eclipse glasses were and how to use them. The talks also encouraged people to stay indoors if they did not own a pair of protective spectacles. Eclipse glasses were being sold at 2500 Malagasy Francs a pair (approximately a day's pay). Cost was evidently a problem for some.

I feel comfortable inferring from the article that eclipse glasses are beneficial for helping to prevent eclipse related retinopathy.

Ironically, I have pair right here on my desk (not the exact same brand though). I used them last year to watch the Venus transit*.

I'm pretty sure they can be mostly safe, but you should follow precautions. The brand I have recommends a maximum of 3 minutes continuous viewing. There are warnings and instructions printed on them.**

The way I used them, I would observe the sun for about 15 to 30 seconds or so at a time, and then take a several minute break in between.

On a different method, the pinhole, projection method is great for eclipses though (pinhole projection doesn't involve special glasses but rather projects an image of the sun on a screen). I highly recommend that as an alternative if not a replacement. But pinhole projection wouldn't work for the Venus transit.

*(Maybe it's about time I tidy up my desk).

**(Make sure you read the instructions and warnings before you use the eclipse glasses. Otherwise, if you happen to misuse them and do something stupid, you might not be capable of reading the instructions and warnings afterwards, inhibiting 20/20 hindsight.)

call me paranoid but I still prefer to project those sort of images on a screen rather than look directly at them.

I don't know how the price would compare, but a good quality welding mask works just fine.

Danger said:

I don't know how the price would compare, but a good quality welding mask works just fine.

'Should be okay for limited intervals with a shade 14 or darker.

Note that there are many different kinds/shades of welding masks/goggles. Many are lighter than this (shade 14) and should not be used for solar viewing.

I have a solar filter that I equip to my telescope to occasionally view the sun. I was a bit nervous before using it, and your fear is largely justifiable, but so long as you purchase eclipse glasses (or in my case, a solar filter) from a credible source, and follow any necessary precautions, then you have nothing to worry about.

Eclipse glasses may be no more than tinted mylar. As long as you keep those glasses in their protective sleeves and prevent scratching of the tint, you should be fine. I have a a 14 darkness glass welding-mask filter, and that is safely tucked away with my astronomy gear. Works just fine.

Astrum said:

From what I've been told, everyone has at least 3-6 "holes" in the retina, from looking at the sun as a baby (I guess it takes them 3-6 times to figure out "looking at the sun = BAD").

I find this hard to believe. The eye does not concentrate light from the Sun into a tiny concentrated spot, it literally forms an image of finite size on your retina. If looking at the Sun burned your retina I'd expect it to have BIG holes, or some other type of damage, which should be pretty obvious to both yourself and a doctor.

In fact, I think I remember a discussion here on PF where someone stated that the amount of light falling onto the retina was incapable of 'burning' it, and it was in fact the UV light that damages your eye when you stare at it. But I wouldn't put on UV blocking glasses and stare at the Sun just because I said so. Better safe than sorry!

collinsmark said:

On a different method, the pinhole, projection method is great for eclipses though (pinhole projection doesn't involve special glasses but rather projects an image of the sun on a screen). I highly recommend that as an alternative if not a replacement. But pinhole projection wouldn't work for the Venus transit.

Projecting the image through a telescope onto a piece of paper works great, too. And that method worked great for the Venus transit.

It's probably not a good idea to aim the telescope at the Sun for a long time, though, as the heat can damage the adhesives that hold the eye piece elements together (unless you're sure you have an eyepiece with no cemented lenses). In any event, risking damage to your telescope is a better option than risking damage to your eyes.

*How to line up your telescope on the Sun without looking through the eye piece? Use the telescope's shadow! If you're lined up on the Sun, the shadow will reduce to a circle.