How to watch a solar eclipse safely - and basics of what an eclipse is
This is from NASA, essentials of the 2017 eclipse same idea for 2024. Just the path of totality is different
Video: Get Ready for the 2017 Solar Eclipse
This is a good explanation of how solar eclipses work from National Geographic which uses part of that video from NASA.
If you want to enjoy the eclipse to the maximum you need to be in a place where the shadow passes over, or you will only see a partial eclipse, with a little sliver of the sun showing throughout.
But if you are lucky enough to be on the path of totality and lucky enough to have clear skies, you see one of the wonders of nature.
The total eclipse is much fainter than the partial eclipse and easily blocked out by a small cloud. While you can see the partial eclipse through light cloud and if it’s a cloudy day with gaps in the cloud you are likely to see it from time to time as it lasts for a fair while. The total eclipse only lasts for minutes.
Here are the stages of a solar eclipse:
see: djmccrady/36336061393/in/pool-lookingtotheskypool
(Photo: Don McCrady, Flickr, CC BY NC ND 2.0)
If you are outside the Moon’s shadow as it passes across the Earth you just see more and more of the sun get blocked out until it is just a sliver then the sun reappears again.
You need to be careful not to stare at the sun - best to use solar eclipse glasses which filter the sun down to be safe to look at. Most people don’t get harmed but if you have a crowd of thousands staring at the sun for minutes on end you can be sure that a few will be temporarily blinded and some may get permanent damage to their eyes. It isn’t total blindness, what happens is you lose vision in the center of your retina, the part you use for reading. So you’ll still have peripheral vision but will find it hard or impossible to read.
There is no harm glancing at the sun for a few seconds as we do anyway in normal life, the issue is if you stare at the sun.
So, stare at it with proper eclipse glasses, or you can look out for the crescent shaped dapples in the shadows of trees or project the sun’s image through a pinhole onto a sheet of paper.
Photo from here: File:IMG 1650 zonsverduistering Malta.JPG So you can look out for those Making eclipse magic
I talk here about what you need to look at the sun and some of the things you can see.
. Robert Walker's answer to What does NASA recommend is the safest way to view the solar eclipse?
But if the shadow passes over you, that is when the magic starts.
You see the diamond ring effect first, where there is just one bright spot of the sun just before it vanishes and the faint glow of the solar corona outlining the rest of the moon. Then the sun completely disappears, and you see the glory of the corona spreading across the sky around the moon.
If you look closely around the rim of the sun you may see red prominences.
.. File:Solar eclipse 1999 4.jpg - Wikipedia
So - this is something beautiful and wonderful. Like a waterfall is beautiful.
Text on graphic: an eclipse is a wonder of nature like a waterfall. Never anything to be scared of.
Photo from: File:Cascada Dynjandi, Vestfirðir, Islandia, 2014-08-14, DD 136-138 HDR.JPG - Wikipedia
“ECLIPSE GLASSES” - EASY WAY TO OBSERVE SAFELY
What most people do is to get eclipse glasses. They make the sky very dark. You just see blackness apart from the sun.They normally tint the sun yellow-orange. It’s not really that colour at all, it’s white. But people expect it to look yellow, and so the manufacturers of these glasses tint them accordingly.
These are very low cost, just a few dollars, so it’s worth ordering a few in advance for yourself and for anyone else who might watch it with you. Or you may get them for free with an astronomy magazine. Be sure not to use them though if they have been damaged and have holes in them, even tiny chinks, and get from a reputable seller.
Be sure to get good quality ones certified to ISO 12312-2
https://luntsolarsystems.com/product/lunt-solar-eclipse-glasses-5-pack/
You buy them in a pack of 5 - that could be useful if you damage one of them, or a friend wants to look at the sun too - anyway they are low enough in cost.
There is a list of sites here that are recommended by the American Astronomical Society: Astronomers just approved more safe solar glasses vendors for eclipse watchers (though some are broken links as that was published in 2017) - that was one of their recommended manufacturers.
I would order the eclipse glasses as a minimum right away if you think there is a chance that you will decide look even once more for more than a few seconds. Doing it before without damaging your eyes permanently doesn't mean next time will be safe. It is also possilble your vision has degraded already with the previous times you did it and you haven't yet noticed and it needs to heal.
NOT SAFE TO USE DARK PLASTIC WRAPPERS, OR LOOK THROUUGH CLOUDS OR REFLECTED IN WATER
It is not safe to use dark plastic wrappers and the like to block out the sun. They may or may not block out the necessary frequencies and as they are not designed for that, there is no way to know.
You can use welder’s goggles but you need to be sure to get the right grade of filter.
Welding filter needs to have shade number at least 12, NASA advice here:
"If it's less than 12 (and it probably is), don't even think about using it to look at the Sun. Many people find the Sun too bright even in a Shade 12 filter, and some find the Sun too dim in a Shade 14 filter — but Shade 13 filters are uncommon and can be hard to find."
https://eclipse2017.nasa.gov/safety
Also stacking lower grade welder glass is not safe.Things like sunglasses and mylar balloons, food wrappers etc are definitely not safe. It’s far easier and safer just to use the proper eclipse glasses.
Many people think it is safe to look at the sun reflected in a puddle or a bucket but that’s not safe either.
It's the UV that causes most damage and you can't see it.
It's the same with looking at it through clouds. Even when the sun is quite dim because of a cloud in between, the UV may still be getting through.
Your eyes aren't affected until a bit of time after you watched it and people who are unlucky find their eyesight in the center of their vision gradually fades. Most recover over a period of days to months.
If you have a large crowd all staring at the sun you can expect a few people to have permanent eye damage, as with this crowd of 10,000 who stared hoping for a miracle, instead a few went blind: It's no miracle, I could see but now I am blind. While others can watch for a long time without any harm.
In one experiment, 3 people whose eyes were about to be removed for medical reasons stared directly at the sun for an hour. They recovered full eyesight in one day, or in 2 days for the one who had their iris partially dilated. But others get permanent eye damage within minutes.
From: Galileo, solar observing, and eye safety
[more details below]
So you could easily be like them and be fine - but just because someone else stared at the sun and was safe doean’t mean you will be as some people get their eyes damaged really easily by staring at the sun.
For more do’s and don’t’s see
ASTRONOMY NOW: Eclipse dos and don’ts
PINHOLE CAMERA - SUN LIKELY DIM - BUT TRY A COLANDER - HELD A LONG WAY AWAY FROM THE SHEET YOU PROJECT ONTO - OR PROJECT IT ONTO PAPER USING THE EYEPIECE OF A TELESCOPE BUT WITH SOME HEAT PROTECTION FOR THE TELESCOPE
You can make your own simple pinhole camera to look at the sun projected onto a sheet of paper (say).
The sun from a pinhole camera is likely to be dim.
For a brighter sun,, if you have a telescope, set up your telescope to look at the sun and then project the image onto a sheet of paper. Of course never look through the telescope viewfinder at the sun.
You need to be careful you don’t damage the telescope optics.
So you need some kind of a heat shield, to reduce the aperture of your telescope. Instructions here from Sky at Night. .skyatnightmagazine.com/feature/how-guide/how-make-solar-projection-screen
This is what it is like - you’ll see sunspots too:
COLANDER - A COOL WAY TO SEE A PARTIAL ECLIPSE
Here is a video
. Easiest & Coolest Pinhole Solar Eclipse Viewer -- Very Cool With a Drill Bit Gauge or Colander
SOLAR SAFE BINOCULARS
The next step up from eclipse glasses is solar binoculars - this is for the PARTIAL eclipse stage.
For the total eclipse, you can use normal binoculars for as long as the corona is showing but be sure to remove them before you see the sun again.
SOLAR OBSERVING TELESCOPES
You can also get a dedicated solar observing telescope or add a filter to use a normal telescope for solar observing.
Telescope owners can use a filter that goes over the the front of your telescope which blocks out 99.99% of the incoming light. However, don’t try a filter at the eyepiece end.. A filter over the eyepiece can be burnt. Don’t try looking through a telescope or binoculars with eclipse glasses. They aren’t designed for that.
Some telescopes used to come with eyepiece solar filters. They are not safe, throw them out..
VIDEO BY AN ASTRONOMER ON HOW TO OBSERVE THE SUN SAFELY - AND WHAT’S UNSAFE
Here is a video on safe and unsafe ways to do i it.
The only time it’s safe to look directly at the sun during an eclipse is when the rest of the sky goes dark and the sun’s corona shows. Before that you get the diamond ring effect - even though it’s just a chink of sun, it’s still not okay to stare with naked eye vision. Your pupils are wide open and your eyes are vulnerable.
You might wonder, what about all the people who stare at the sun at sunrise and sunset?
Well the sunlight gets to you almost horizontally through the thickest part of the atmosphere, and there are often clouds in the way. Even so, people don’t tend to stare at the sun for long. They look at the clouds and many other things. And unlike a total eclipse, it’s still quite light so your pupils are contracted too.
When you watch a solar eclipse, even a partial one, your attention is all on the sun, and if it is a total eclipse or close to, then your pupils will open wide.
WHERE TO SEE THE ECLIPSE
CHECK THE WEATHER
There’s a significant chance of cloudy weather on April 8th which often means you miss the total eclipse. It goes dark but you don’t see the sun or corona.
As of writing this the best weather is in New York state a bit surprisingly or Indianapolis. But this is sure to change.
. NOAA NWS Weather Prediction Center
SUNGAZING AS A RELIGIOUS OR HEALTH PRACTICE AT SUNRISE AND SUNSET
It’s not a good idea to stare at the sun even at sunrise and sunset either - yes the light is somewhat more filtered but it’s NOT as good as looking at the sun through a safe solar filter.
You might be one of the few whose eyes are particularly susceptible to this. Some people stare at the sun as a religious observance of sungazing especially at sunrise and sunset or for their alleged health benefits. It’s an alternative healing method.
But the sun isn’t guaranteed safe at sunrise or sunset. Compare what you see at those times with what you see with eclipse glasses.
And maybe many of them do it just fine - this chap seems to have managed okay - but you might be one of the unlucky ones, as doctors occasionally see patients with eyes damaged through these religious observances.
Here is an example, of five patients treated for serious eye problems after attending a gathering of 10,000 catholics staring at the sun hoping to see a miracle. The Catholic Church warned them against attending according to this article but many did anyway and a few went blind: It's no miracle, I could see but now I am blind -
There again that’s 10,000 people and presumably they didn’t all go blind, but five, at least, did. Temporarliy anyway, and some of those might have lost some of their sight, in the area used for detailed vision and reading, permanently. If you are unlucky, you could lose the ability to read through this practice, as Isaac Newton did, temporarily, or permanently.
COULD YOU SUBSIST ON SUNLIGHT ALONE THROUGH SUNGAZING?
Some practitioners from India think it is possible to live only on sunlight, without eating, and some of these engage in sungazing.
This doesn’t make scientific sense, so if they are able to do this, it’s basically a miracle, something science can’t explain. The cells at the back of our eyes may actually get a tiny amount of energy from sunlight. There are some microbes, the haloarchaea that obtain all their energy from sunlight not by photosynthesis, but by a process very similar to the way that we see. They use bacteriorhodopsin, and our eyes use rhodopsin. It’s much the same.
.. Lake Hillier in Western Australia, a "pink lake". It's pink partly because of the purple haloarchaea, and partly because of red carotene accumulating in a green algae dunaliella salina.
The green algae use chlorophyll. But the haloarchaea use rhodopsin and don’t fix carbon dioxide or generate oxygen but convert light directly into energy via a “proton pump” in much the way that our eyes use to see sunlight.
But that’s just one tiny bacteria subsisting off sunlight, which indeed they can do, just fine. Perhaps the cells at the back of your eye could subsist off sunlight, but not your whole body, at least not according to scientific understanding.
There’s no way, scientifically, that your entire body could subsist from photosynthesis through your eyes. See also Sungazing - RationalWiki
Also it’s not safe to stare at it through light cloud or to stare at its reflection in a mirror or in a bowl of water.
Most of the dangerous rays of light are invisible to your eyes, and for instance a cloud that blocks out the sunlight in visible light might let the dangerous UV light through.
MEDICAL EXPERIMENT STARING AT THE SUN FOR ONE HOUR
From: Galileo, solar observing, and eye safety
“Tso and Piana asked three middle-aged people, each with an eye that was to be surgically removed to prevent the spread of malignant melanoma, to stare directly at the Sun for one hour, a day or two before the operation. To quote from their summary:
“Two of the patients sungazed with an undilated pupil, and, 24 hours later, recovered their preexposure visual acuity with no detectable scotoma. One of the patients looked at the sun with a partially dilated pupil, and 24 hours later her visual acuity dropped from 20/20 to 20/25.
“But even in that eye, whose pupil was dilated to 4 mm, acuity was back to 20/20 after another day, though the scotoma remained.
“After surgery, the eyes were examined under the microscope. Although damage to the retinal pigment epithelium was seen in every case, the photoreceptors appeared perfectly normal. The ages of the patients were 49, 55, and 57 years.
“On the other hand, there are also cases of people who stared at the Sun for only a few minutes, when it was much lower in the sky, and suffered long-lasting scotomas:”
NEWTON’S TEMPORARY BLINDNESS - UNABLE TO READ
Newton reports that he damaged his eyes to the extent that he couldn’t read, by staring at the sun, which he did repeatedly over a period of some hours, after which he stayed in total darkness for three days to try to recover. He eventually did but for some months later he still saw effects from his eye damage in dark conditions. You can read the details here: Eye problems of other early solar observers
You might well be okay like Newton eventually - but there again you might not.
DON’T EVEN GLANCE AT THE SUN THROUGH A TELESCOPE UNLESS SET UP FOR SOLAR OBSERVING WITH THE PROPER FILTERS OVER THE OBJECTIVE - BURNING LENS EXPERIMENTS
It’s especially important not to look through any kind of telescope or binoculars. In that case, it’s the infrared more than the UV, it can literally burn your retina.
This is why you must not look at the sun through a telescope unless it has a properly installed solar filter:
SUMMARY
So for most of us, the advice is to use the proper eclipse glasses to look at the sun, and only take them off for the solar corona. Or of course to look around at the crescent dapples etc. And be ready to put them back on as soon as the diamond ring effect appears again. As for projection, looking through a telescope etc - maybe you can some nearby astronomers with telescopes to show it to you through their scopes?
But you don’t need to be like David Mitchell
It’s okay to glance at the sun as happens normally in daylight.. It’s staring for it for long periods that’s the issue and this is something we don’t normally do except during a solar eclipse. Normally you can just rely on what comes natural to you, it’s so bright you just look away again naturally, unless you deliberately stare at the sun, and your eyes are kept safe.
The safety tips for observing the sun are due to accidents that happen to only a few people out of thousands, (at least 5 out of 10,000 for that Catholic sun gazing miracle seeking crowd). But they do happen, which is why doctors warn us not to stare at the sun. They want us to be safe and not be one of the people in that statistic which leads to them having to treat patients with sometimes irreversible eye damage.
And - just never look through binoculars or a telescope even for a fraction of a second, except during the solar corona. When you see the corona it is safe to look even through a wide aperture high power telescope. But you need to keep an eye on the time and be sure to look away in good time, e.g. 30 seconds before totality is due to end or some such.
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