Eye protection while watching a total solar eclipse

I got myself some glasses for the upcoming solar eclipse, but they are very dark! They work fine for looking at the Sun in all its glory, but I suspect I won't ne able to see anything of interest during the eclipse.

Does anyone have experience filtering out the harmful UV while still being able to see something during the eclipse?

They should be fine for everything other than totality. I used some to watch the annular eclipse a few months ago and it was fantastic. For totality, I don't think you need any protection.

DrClaude said:

I got myself some glasses for the upcoming solar eclipse, but they are very dark! They work fine for looking at the Sun in all its glory, but I suspect I won't ne able to see anything of interest during the eclipse.

Yes, good safety glasses are too dark to see anything except the sun (and corona?). You should plan to take them off and on. It's nice to look around and see other effects. The shadow patterns through leaved trees are fascinating. Apparently, animals also react strangely.

DrClaude said:

Does anyone have experience filtering out the harmful UV while still being able to see something during the eclipse?

I don't know if those fast reacting welding masks may be safe and allow you to look around. Welding masks with shade numbers of 12 to 14 are supposed to be safe.

Personally, I would just flip the glasses up and down.

PS. I will miss both total eclipses. I was in Fort Worth when it was total in the Northwest and I am now in the Northwest when it will go through Fort Worth. :-(

FactChecker said:

Welding masks with shade numbers of 12 to 14 are supposed to be safe.

I believe one needs to be careful with autodarkening ones. My welding helmet will darken when first placed in the solar flux but seems to respond only to the fluctuation (AC) to maintain (and recalculate) the darkening ongoing. So better to use a simple old-fashioned welding glass. Beware.
https://www.garagejournal.com/forum/threads/welding-helmet-eclipse-fail.368737/

DrClaude said:

I got myself some glasses for the upcoming solar eclipse, but they are very dark! They work fine for looking at the Sun in all its glory, but I suspect I won't ne able to see anything of interest during the eclipse.

Does anyone have experience filtering out the harmful UV while still being able to see something during the eclipse?

NASA Guidance: https://science.nasa.gov/eclipses/safety/

To put it simply: you wear eclipse glasses during the partial phases and take them off during totality.

I am organizing a grass roots effort to help prevent blindness in wildlife during eclipses. It has been pretty unsuccessful so far, but we hope to improve our success rate in this upcoming eclipse across the US. You can sign up at the link below if you are willing to help. Your rabies vaccinations must be up to date, BTW.

Sign up here


https://www.cnn.com/2024/03/13/world/eclipse-zoo-animal-behavior-nasa-soundscapes-scn/index.html

Tortoises start to mate when it gets dark? This is news? They should bring out a bottle of wine and play some Marvin Gaye and see what happens.

Follow-up question:

During totality, it is safe to view the eclipse directly; it is also safe to remove the solar filter from a telescope/lens. What about extended viewing through binoculars? I don't know what the optical properties of the corona are (e.g. spectrum) and so wonder if increased UV dose is a possibility.

Andy Resnick said:

Follow-up question:

During totality, it is safe to view the eclipse directly; it is also safe to remove the solar filter from a telescope/lens. What about extended viewing through binoculars? I don't know what the optical properties of the corona are (e.g. spectrum) and so wonder if increased UV dose is a possibility.

BE CAREFUL! Telescopes and binoculars gather MUCH MORE light than the naked eye. You can do real damage in a split second.

The corona is very, very hot. Its thermal spectrum peaks in the x-rays. Plenty of UV. Fortunately, it is not very bright.

The problem with "I'll only look during totality" is that there is no warning that totallity is going to end. Bailey's Beads are bright and I would say they last a second, possibly less. Then the sun gets even brighter.

This is a huge risk. I wouldn't take it. If forced, I'd wear a patch over one eye, so I'd at least have one left.

Andy Resnick said:

Follow-up question:

During totality, it is safe to view the eclipse directly; it is also safe to remove the solar filter from a telescope/lens. What about extended viewing through binoculars? I don't know what the optical properties of the corona are (e.g. spectrum) and so wonder if increased UV dose is a possibility.

That's an extraordinarily interesting question, IMHO, as when I plug the different temperatures for the sun(5800 K) and its corona(3,000,000 K) into my Planck's Law spreadsheet, the difference between the two tells me that looking at the corona is between 3500 (@ 800 nm) and 54,000 (@ 400 nm) times as intense*. Yet, everyone and their mother says it's just fine to look at the total solar eclipse for as long as you like.
IMHO, your question might require its own thread, as the paradox just gets worse.
Unless of course someone can succinctly explain why, according to Plank's law, the sun's surface provides the earth with 1000 w/m² of power, the sun's corona provides the earth with 15,000,000** w/m² of power, yet we are not all dead?

*When measuring the 'B' value: W/m²/sr/nm
**Just a ballpark figure, as I'm extraordinarily bad at maths.

Vanadium 50 said:

I'd wear a patch over one eye, so I'd at least have one left.

Best advice yet. :-)

I have heard that some people use X-Ray or CT-scan reports (what's that black film called?) to view eclipses. I don't know how well they work though?

FactChecker said:

Best advice yet. :-)

It also is good for National Talk Like A Pirate Day. Arrggghhhh....

OmCheeto said:

Yet, everyone and their mother says

A fine PF source...

OmCheeto said:

Unless of course someone can succinctly explain

Because the corona is extraordinarily diffuse. It has a high temperature, but very little heat. Same reason you can out you hand in a 400 degree oven (without touching anything) with no problem, but not a pot of 212 degree boiling water.

Note that the sun's surface is right next to the corona. and the corona doesn't heat it up. They aren't even in equilibrium.

OmCheeto said:

That's an extraordinarily interesting question, IMHO, as when I plug the different temperatures for the sun(5800 K) and its corona(3,000,000 K) into my Planck's Law spreadsheet, the difference between the two tells me that looking at the corona is between 3500 (@ 800 nm) and 54,000 (@ 400 nm) times as intense*. Yet, everyone and their mother says it's just fine to look at the total solar eclipse for as long as you like.

Vanadium 50 said:

Because the corona is extraordinarily diffuse. It has a high temperature, but very little heat. Same reason you can out you hand in a 400 degree oven (without touching anything) with no problem, but not a pot of 212 degree boiling water.

Yeah, that's about what I thought. According to exposure tables, the corona is 17 stops slower than the photosphere. 17 stops = optical density 5, so the total amount of light coming from the corona is 0.001% of the light from the photosphere. That's why it's safe to look at it unaided.

In terms of the relative spectra, if coronal UV light output is truly 50000x more than the photosphere (and that is something I am unable to verify), then the emitted UV from the corona is half the amount as compared to the UV emitted from the photosphere, which would indicate that observing through a lens is not advised (and probably not naked eye, either....), but UV photography of the corona could be interesting to try out, if you have the equipment.

I'm skeptical of the 50,000 number- I think it should be lower- but I have no alternate suggestion.

Andy Resnick said:

I'm skeptical of the 50,000 number- I think it should be lower- but I have no alternate suggestion.

That is surely an approximation. The corona isn't even in thermal equilibrius with itself, so it doesn't really have a temperature. There is also an inner and outer corona, and the (bright) inner one is at least partially obscured by the moon.

Also - and this is not safety advice - glass is opaque to short-wavelengty UV.

Vanadium 50 said:

That is surely an approximation. The corona isn't even in thermal equilibrius with itself, so it doesn't really have a temperature. ...

Doesn't have a temperature? NASA says it's around 3,000,000 °F

@ ≈2:30 in the video

There is another thread on this. The electrons have a temperature, the protons have a temperature, the heavier ions have a temperature, and these are all different numbers.

FactChecker said:

BE CAREFUL! Telescopes and binoculars gather MUCH MORE light than the naked eye. You can do real damage in a split second.

Yes, I had a solar filter crack once when my eye was not looking through the eyepiece. I was lucky. you might not be.

Vanadium 50 said:

Also - and this is not safety advice - glass is opaque to short-wavelengty UV.

Some glass is, many types of glass are not. Plexiglass (PMMA) is very much opaque to UV via absorption.

For sure when you are trying to get UV through your optics, glass is always more opaque than you want.

You can find plenty of transmission curves on the web.

I dug out the horrible static UV filter/shield that came with my Harbor Freight stick welder and looked at the sun. I declare it sufficiently dark.....sun very dim and no afterimages on my aging retinas. I believe it is marked as a number 11. However, I do bump into terrestial objects without any optical inhibition. Very dark indeed and shin damage more likely than retinal damage.

hutchphd said:

I dug out the horrible static UV filter/shield that came with my Harbor Freight stick welder and looked at the sun. I declare it sufficiently dark.....sun very dim and no afterimages on my aging retinas. I believe it is marked as a number 11. However, I do bump into terrestial objects without any optical inhibition. Very dark indeed and shin damage more likely than retinal damage.

Welding masks with shade numbers of 12 to 14 are supposed to be safe. I'm not sure if you can tell when UV is damaging your eyes. Some sunburn damage does not show up for a few hours. I recommend playing it safe.

Andy Resnick said:

What about extended viewing through binoculars?

DONT do it !!, please dont ... as per post #9

Dave

OmCheeto said:

IMHO, your question might require its own thread, as the paradox just gets worse.
Unless of course someone can succinctly explain why, according to Plank's law, the sun's surface provides the earth with 1000 w/m² of power, the sun's corona provides the earth with 15,000,000** w/m² of power, yet we are not all dead?

I know about this from photography. The color temperature of a light source tells you the black body temperature where the light was created. It has nothing to do with how much power the light itself has where you are. (LED lamps aren't black body, so ignore them for this discussion.)

For example: If a lamp has a 3200° kelvin color temperature, and you filter out 90% of the light entering your camera, what is left will still have the same 3200°k temperature. It will just be dimmer. Fewer photons, but the same range of frequencies. You can make the color temperature of a lamp go up by passing the light through a bluish filter (CTB) to reduce some of the lower frequencies. This would change the light's color to more closely resemble daylight. But it would still be dimmer because you have still reduced the total number of photons.

So you can't multiply the light output by 50000x simply because the color temperature is higher. The corona is extremely hot, but there are very few actual atoms there. Those atoms produce high frequency photons, but nowhere near as many photons as the sun's surface does.

davenn said:

DONT do it !!, please dont ... as per post #9

Dave

Sigh... obviously that's good advice pre-and post- totality. I was asking about during totality.

Besides, there are plenty of solar-viewing binoculars on the market- those are to be used pre-and post-totality.

Again, I was asking specifically about viewing during totality.

FactChecker said:

Welding masks with shade numbers of 12 to 14 are supposed to be safe. I'm not sure if you can tell when UV is damaging your eyes. Some sunburn damage does not show up for a few hours. I recommend playing it safe.

Welding masks with shade numbers between 12 and 14 are considered acceptably safe- as long as they are arc-welding shades and not auto-darkening (or made for gas welding).

https://eclipse.aas.org/sites/eclip...Tech-Report-Solar-Eclipse-Eye-Safety-2023.pdf

Also, don't put one in front of a lens for photography- the optical quality of the shades are poor and will distort your image.

Andy Resnick said:

Again, I was asking specifically about viewing during totality.

But that is the problem. Totality ends so fast and suddenly that with binoculars you'd have eye damage before you can blink.

Algr said:

But that is the problem. Totality ends so fast and suddenly that with binoculars you'd have eye damage before you can blink.

If an auto-darkening welding mask is not fast enough, then you will not be fast enough. They go dark in 1/10,000 to 1/25,000 sec.

The safest way is to not look into the sun directly, even with protection glasses, but to look instead at the live broadcast:
https://svs.gsfc.nasa.gov/14520/

Here is a video from B&H Photo Video about photographing the total eclipse. It's not clear to me if it is only for the minute or two of totality.

A danger is, if the moon blocks only 99.9 % of the sun, that the eyes can be destroyed for the rest of your live without proper filter, as the video states.

• In such a situation, the sharp borderline between moon and sun triggers, that the eyes auto-focus to infinity, which destroys the retina in the eye.
• Also the eyes widen and let more light in while an eclipse, because the overall luminous flux is small. But the luminous flux per unit area is the danger in this case.

That's even more dangerous than looking into the normal sun without eclipse. But also this can destroy the eyes.

I choose the safe way and look never directly into the sun or other light sources. Also, I don't trust "ISO-certified" filters. Who knows.

Sagittarius A-Star said:

Also, I don't trust "ISO-certified" filters. Who knows.

Get the glasses from a trusted supplier on this list.

FactChecker said:

Get the glasses from a trusted supplier on this list.

That may reduce the risk.

Unfortunately, you can't check whether a filter meets the ISO standard yourself — doing so requires a specialized and expensive piece of laboratory equipment called a spectrophotometer that shines intense UV, visible, and IR light through the filter and measures how much gets through at each wavelength. Solar filter manufacturers send their products to specialized labs that are accredited to perform the tests necessary to verify compliance with the ISO 12312-2 safety specifications. Once they have the paperwork that documents their products as ISO-compliant, they can legitimately claim to meet the standard on their products and packaging.

Even more unfortunately, unscrupulous vendors can grab the ISO logo off the internet and put it on their products and packaging even if their eclipse glasses or viewers haven't been properly tested. This means that just seeing the ISO logo or a label claiming ISO 12312-2 compliance isn't good enough. You need to know that the product comes from a reputable manufacturer or one of their authorized dealers.

Source:
https://eclipse.aas.org/eye-safety/iso-certification