Viewing the eclipse

There is going to be an eclipse tomorrow and I’m hoping I’ll get to take a look at it. I remember hearing somewhere that it is safe to use a the magnetic media inside a 3.5" floppy as a filter to look at the eclipse. Is that true? If I look at the eclipse through a couple of 3.5" disks would that be enough protection?

Totally unsafe.

The best way to view the eclipse is with a welding mask of the highest protection level. They are cheap and very safe. Only problem is that the sun will appear with a green tint.

What time is the eclipse supposed to happen?

Don’t risk damage. I know of people with permanent injury from being stupid. The risk with many dark filters is that they dim the visible light, but transmit enough IR or UV to cause permanent damage.

Here is a reasonable guide to safe options.

Yep. I bought a welding helmet lens big enough to put over my camera lens to take pictures for six bucks. Get shade 13 or darker (higher numbers). The only issue is that it was the last piece in the store and that was two weeks ago. You might have trouble finding one.

When I was a kid I used one of dad’s welding lenses. Last time I watched an eclipse, I hadn’t had a welding lens for a couple of decades. I used a 5-1/4" floppy disc. (3-1/2" discs were still being used at the time.) I’m not blind.

Here you go.

Around 6PM here in CA. If you are in MT, don’t expect to see much.

ETA: I was lucky enough to be smack dab in the middle of one when I was younger. It’s amazing how much of the sun can be covered before you notice it.

Yep, two problems here: 1) At the 49th Parallel we’re too far north; 2) On the Salish Sea we’re expecting low clouds. I don’t expect to see anything, let alone ‘much’.

OK, but seriously—what’s the worst that could happen if you just looked for a couple of seconds and looked away? Serious question.

I was on a train the whole time and didn’t see much, but I tried that about 6 minutes after the eclipse started. It was too painful; I had to look away immediately. I thought we were supposed to get something like 80% coverage here in Southern California, but I didn’t really see much of anything different out the windows of the train. My sister in Texas said it was “eerie dark” outside though. She texted me at 5:25 PST.

Very little. The danger with partial solar eclipses is that that eventually the overall brightness is too low to trigger a pain reflex, and it becomes possible to look for an extended period at the remaining solar disk. However the surface brightness of that remaining sliver of disk is still full solar brightness, it can, and will, cause permanent damage.

Same problem for filters that only block out visible light. You can look for extended periods and not feel any pain, despite significant damage being done.

When I was a kid and we had an eclipse my father had us watch through, I guess you would call it, a camera obscura.
He took a box put a small hole in one end, he had us put the box over our head facing away from the hole. Then we lined up the box so the image of the sun was projected on end we were facing.
No UV entering the eyes.

Here’s the best resource I could find: NASA - Annular Solar Eclipse of 2012 May 20

Shade 10 is considered adequate for TIG welding, which is about as bright as you get when welding. Do you really need 13 for watching the sun? at least one layer of the lens stack is likely to be polycarbonate, which should block pretty much all of the UV; I was under the impression that the tint level was primarily to control the intensity level of the visible wavelengths.

This is of interest because I have a couple of welding masks, one of them an LCD/autodarkening model, and I planned to use them to watch the eclipse tomorrow.

Viewing the sun directly requires a #14 welding glass filter. Lesser numbers or polycarbonate filters are not sufficient and could allow eye damage.

I bought eclipse glasses from the museum. Cheap and easy - check your local museum or planetarium. No guarantees they won’t be sold out.

Are you talking about this eclipse?

You must have a time machine.

Eye Safety During Solar Eclipses by B. Ralph Chou, MSc, OD

Exposure of the retina to intense visible light causes damage to its light-sensitive rod and cone cells. The light triggers a series of complex chemical reactions within the cells which damages their ability to respond to a visual stimulus, and in extreme cases, can destroy them. The result is a loss of visual function which may be either temporary or permanent, depending on the severity of the damage. When a person looks repeatedly or for a long time at the Sun without proper protection for the eyes, this photochemical retinal damage may be accompanied by a thermal injury - the high level of visible and near-infrared radiation causes heating that literally cooks the exposed tissue. This thermal injury or photocoagulation destroys the rods and cones, creating a small blind area. The danger to vision is significant because photic retinal injuries occur without any feeling of pain (there are no pain receptors in the retina), and the visual effects do not occur for at least several hours after the damage is done [Pitts, 1993].

You can do pretty well with two sheets of paper. Poke a tiny hole in one a project the image onto the other. I have viewed several partial solar eclipses this way. You can see a clear disc of the sun with a bite taken out of it. The image is small but I found it clear.

In a total solar eclipse it’s perfectly safe to view it directly without protection (during Totality only), since the sun itself is not visible. This eclipse, however, will be an “annular” eclipse, in which a tiny ring of sun will still be visible around the moon . . . so it will never be safe to look at it directly.

It’s always dangerous to look directly at the sun. There’s nothing special about an eclipse; when you’re looking at the uncovered part of the sun, it’s the same as looking at it any other time. The only difference is the number of people looking.

And bear in mind that the biggest danger is looking at it through magnification, like a camera zoom.