I remember from perhaps 50 years ago using 35 mm B & W film that had been exposed to sunlight for 60 seconds and then developed to view the partial solar eclipse which presented around Washington, D.C. We used a layer three or four thick and it worked out well. 35 mm film is not particularly easy to come buy these days. What I do have is maximally exposed laser image x-ray film which seems to be a fine substitute. And yet several websites caution against using exposed x-ray film. My feeling is that this may be do to the fact that it is NOT safe or perhaps simply because they don’t want people looking up through the heart portion of a chest x-ray. I think the latter is the reason. I am having trouble relating opacity data on black x-ray film with ISO 12312-2 international standard. Can anyone help me with this.
Best is #13 welding glass, or a pin-hole camera … and this is only for the partial phases, which aren’t all that exciting … during totality eye protection isn’t necessary …
You can test your exposed film idea by briefly trying today, just a quick glance shouldn’t harm your eyes … but generally speaking, what ever contraption you come up with take more time and money than a pin-hole camera …
You can’t go just by how dark it looks, because there’s danger from the infrared and ultraviolet, too, and you can’t tell how much of that is making it through your makeshift filter. Doubtless there are some ways that you could improvise a filter which would work, but if you don’t know which of those methods are safe, it’s best not to use any of them.
One danger is that someone might use exposed colour negative film as a filter. This has zero cut in the IR, and so can lead to significant damage.
X-Ray film really has two different forms - the real stuff that is exposed to X-rays, and the modern stuff that is simply exposed to ordinary light in a glorified laser printer. The latter is very thin in comparison to the real stuff. I don’t know how much silver would be in the emulsion, but I bet not much. I would be very hesitant using it.
My mother used the film method a long time ago (maybe for the same eclipse you watched) and ended up with eye damage.
Eclipse glasses are a couple dollars and are probably even available at 7/11’s at this point. Still enough time to order a pair or two online. Why risk your eyes.
I have a large tent. I’m going to wrap it in black visqueen (heavy duty plastic) and create a camera obscura (example). With a magnifying glass at the aperture, I should have a decent, live full-color 12-inch view of the Sun inside my camera tent that I can view and never look at the Sun.
If you really want to try making your own solar filter, Aluminized Mylar (emergency blanket material) is the way to go. The Aluminum is a broad-spectrum mirror, and if pinhole-free, makes a fine solar filter.
Not sure how to phrase this dumb question . . . is added concern about eye protection during an eclipse due to the fact that people might stare at the partially blocked sun longer because they *can *(as opposed to a regular day when one can’t look at the sun for more than a split second) and therefore incur damage? That kind of makes sense but -and here’s the really stupid part- aren’t our eyeballs just as exposed when we walk around without sunglasses on a normal day? I mean, do the bad rays not penetrate regardless if we’re looking straight at it? Sorry of that doesn’t make sense.
You can answer this easily for yourself: can you look at your car sitting in your driveway? Now, can you look up directly at the sun comfortably? If the answer to the first question is yes, and the second is no, then clearly the “bad” rays are not entering your eye when you’re not looking at the sun directly.
Light scatters when it hits things, thankfully, or else we wouldn’t be able to see stuff. But it’s a miniscule portion of the light that arrived from the sun, usually. When it’s not, we often have trouble looking at it (a polished mirror reflecting sunlight, or the sunlight reflecting off of a windshield of a car, etc.). Not only visible light does this; it’s done to some extent by infra-red, ultra-violet, radio, x-ray, etc.
Generally, people don’t stare at the sun.
If you catch a glimpse of the sun directly in your visual field (say while driving, or looking up at a bird), you will instinctively avert your eyes, avoiding damage. During an eclipse, people might foolishly stare at the sun, subverting that protective mechanism.
You can in fact look at the Sun for longer than a split second, on a normal day. It’s painful to do so, and that pain usually encourages people not to do it, but you can.
But when something about the Sun looks really cool, you might disregard the pain for a little longer, in order to get a better view of it. And that’ll cause eye damage.
Thanks, DSYoungEsq
And everyone else
There’s no such thing as a dumb question, only dumb mistakes …
Whether we can look at the sun or not isn’t as important and the eye strain that comes from looking at the sun … we don’t want to fatigue our eyes during the hour and a half lead up to the Main Event … it would be a shame if someone had to cover their eyes with a wet washcloth during totality … the partial phases aren’t worth it …
Isaac Newton temporarily blinded himself by staring at the uneclipsed sun while standing in a darkened room (thereby ensuring that his pupils were dilated), a situation guaranteed to maximize eye damage. He said it took 3 or 4 days to regain some use of his eyes, and several months to return to normal.
And Galileo permanently blinded himself, by looking at it through a telescope.
It should be noted that it’s pretty hard to override your instinct to look away from the sun when it’s uneclipsed. During the partial phase of an eclipse, the total amount of light is reduced, so the instinct to look away is reduced, and it’s easier to stare at it. Thus there are two factors in play – the sun is interesting during a partial eclipse so people WANT to stare at it, and the reduced light makes it EASIER to stare at it. But any portion of the sun that’s not eclipsed, even a tiny sliver, can cause damage to the retina if you stare at it.
For past eclipses I have gotten really good results projecting the image onto a dark board using binoculars.
I found it worked fine even without the cardboard cutout to make a better shadow around the image.
A number of public libraries around the country will be distributing free eclipse viewing glasses. Warby Parker stores also are giving them away.
So is it okay to look at a partial solar eclipse for the length of time that you might normally glance at a brightly shining, uneclipsed sun? Or is there somehow some extra danger in viewing the eclipsed sun other than the temptation to look at it too long because it is darker than the regular sun?
If you go the glasses route (I am) be sure they are ISO certified; there are fakes out there.