Astronomy

Why shouldn't you look at the Sun through a camera using eclipse glasses?

Why shouldn't you look at the Sun through a camera using eclipse glasses?


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One of the NASA approved eclipse glasses manufacturers has the following warning on one of their eclipse glasses:

Do NOT look through a camera, telescope or binoculars with ANY eclipse shades on!

I can see how the enlarged image of the Sun through a telescope or binoculars might overwhelm the eclipse glasses' filters.

But how would looking at the Sun using a camera's viewfinder or LCD screen reduce the effectiveness of eclipse glasses (assuming you're not using any zoom function)?


Electronic viewfinders (such as the ones using LCD or OLED screens) are excluded from this discussion. There's no danger of eye injury there, except perhaps danger of damaging the camera's sensor if exposure is very long and the lens aperture is big.

It's the classic or optical viewfinders that are targeted by the warning.

I can see how the enlarged image of the Sun through a telescope or binoculars might overwhelm the eclipse glasses' filters.

A few observations.

It's really the larger aperture of the instrument that is the problem here. The pupil of your eye is only a few mm in diameter. The objective lens or mirror of a telescope could be anywhere between dozens of mm to hundreds of mm (or thousands for very large instruments). The ratio of areas between telescope aperture and eye pupil is even greater - it's the square of the ratio of diameters.

Let's say your eye's pupil is 2 mm in diameter. Let's say you use a 50 mm aperture telescope (small refractor or binoculars). The diameter ratio is 25x. The area ratio is 625x.

All the light captured by the very large area of the instrument is funneled into your eye through your pupil. With the instrument, now you're getting 625x more energy from the Sun, compared to the naked eye view. It's already dangerous to look at the Sun with the naked eye - with the instrument it's 625x more dangerous. And this is with a very small refractor.

There is a class of "solar filters" that are made to be mounted on the instrument's eyepiece, or after the eyepiece. THESE ARE VERY DANGEROUS! All the increased, focused energy of the Sun is now absorbed by the filter, which can warp, melt, crack, or burst into flames. A filter failure at this point is likely to injure the user. White light filtering for solar observations must always occur ahead of the instrument, not after it.


As for why classic, optical viewfinders were included in that list: it was out of an abundance of caution. Most of those viewfinders do not capture more light than your eye does, but some do. It's better to be safe than sorry. You can't expect everyone to be able to tell whether their viewfinder is dangerous or not. So, in a warning addressed to the general population, just tell them to stay away from it.

Now, if you install a full-aperture solar filter (like the Baader solar film) ahead of the viewfinder, then it's safe to use - provided the filter is attached firmly to the camera and cannot be blown away by some random gust of wind.


Science Says Why We Can't Look at the Sun

During next month's Great American Total Solar Eclipse, you may be tempted to take in the historic event by gazing directly at the sun, but you absolutely should not do this without the proper eye protection, experts say.

That's because, even though the sun is some 93 million miles (150 million kilometers) away, it can still cause serious, and sometimes irreversible, eye damage.

"Even very short direct observation of the sun has the potential to cause damage," said Dr. Russell Van Gelder, a clinical spokesman for the American Academy of Ophthalmology (AAO) and director of the University of Washington Medicine Eye Institute in Seattle. [The 8 Most Famous Solar Eclipses in History]

On Aug. 21, 2017, the moon will pass between the Earth and the sun, causing a total solar eclipse that will be visible from parts of the United States, along a narrow path from Oregon to South Carolina. It will be the first time since 1918 that a total solar eclipse will be visible across the continental United States (from the West Coast to the East Coast), according to the American Astronomical Society (AAS). People outside the path of the total solar eclipse will see a partial solar eclipse.

Regardless of where you observe the eclipse, it's important not to look directly at the sun with the naked eye. To understand why, think of a child using a magnifying glass outside to burn holes in paper. "Focusing the sun's rays on a single point creates a lot of energy," Van Gelder said. And the lens in your eye is about four times as powerful as the type of magnifying glass a child might play with, Van Gelder said.

"If you take a lens that has that much power and point it directly at the sun, the energy becomes very high," and is enough to literally burn holes in the retina, or the light-sensitive cells at the back of the eye, Van Gelder said.

Patients with this condition, known as solar retinopathy, show a very characteristic pattern of eye damage during an exam. "It looks like someone took a hole punch and just punched out the photoreceptive cells in the retina," Van Gelder told Live Science.

It's thought that this damage happens when photons (light particles) create free radicals, which are highly reactive molecules that can "poison" cells and kill them, Van Gelder said. The damage occurs in the fovea, a spot in the retina that is responsible for sharp, central vision. As a result, patients with solar retinopathy may have blurry vision or a central blind point in their eyes, according to the AAO.

Many patients with solar retinopathy recover from their symptoms, but some have lasting vision problems. For example, in a 2002 study of 15 patients in England with solar retinopathy from viewing an eclipse in 1999, all but two had normal vision on an eye exam 8 to 12 months later. Still, even some patients with normal vision on an eye test had subtle eye symptoms, such as a small blind spot in their vision.

In theory, a person could become legally blind &mdash vision of 20/200 or worse &mdash from staring at the sun. But staring at the sun is unlikely to result in total blindness, or loss of both central and peripheral vision, because solar retinopathy typically doesn't damage peripheral vision, Van Gelder said.

Because of the dangers, the AAO recommends that people not spend any time looking directly at the sun with their naked eyes. There is one exception to this rule &mdash if you're in the path of a total solar eclipse, you may look at the sun with your naked eyes during the brief time when the sun is in "totality," meaning the sun's bright face is completely blocked by the moon. (The length of totality will vary depending on where you view the eclipse, but at most, this event will last 2 minutes and 40 seconds, according to the AAS.)

But there is a way to view the entire solar eclipse event safety, using special "eclipse glasses" or handheld solar viewers that contain solar filters, according to the AAS. You'll need to use these glasses if you want to look at the uneclipsed or partially eclipsed sun. The four manufacturers with certified eclipse glasses and handheld solar viewers are: Rainbow Symphony, American Paper Optics, Thousand Oaks Optical and TSE 17, according to the AAS.

It's important to note that you should never look at the sun through an unfiltered camera, telescope or binoculars, regardless of whether you're wearing eclipse glasses. That's because these devices will focus the sun's rays even more than your eyes do, Van Gelder said, and this can cause serious eye injury.

REMEMBER: Looking directly at the sun, even when it is partially covered by the moon, can cause serious eye damage or blindness. NEVER look at a partial solar eclipse without proper eye protection. Our sister site Space.com has a complete guide for how to view an eclipse safely.

Copyright 2017 Live Science, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.


Why Does a Solar Eclipse Damage My Eyes?

According to experts, viewing the sun with your naked eye during the eclipse can burn your retina, damaging the images your brain can view. This phenomenon, known as “eclipse blindness,” can cause temporary or permanent vision impairment, and in worst-case scenarios can lead to legal blindness, which entails significant loss of vision.

“If people look without the proper protection [at the sun], they run the risk of injuring their eyes. And if they get an injury, depending on how often and how long they look at the sun without the protection, they do have a substantial risk of developing a permanent loss of vision,” said Dr. B. Ralph Chou, president of the Royal Astronomical Society of Canada and a former optometry professor. It is not possible to go completely blind from looking at the eclipse, Chou said, because the injury is limited to the central part of your visual field.

There are no immediate symptoms or pain associated with the damage &mdash the retina doesn’t have any pain receptors &mdash so its hard to know at the time if you’ve actually been afflicted with eclipse blindness. If you look at the sun unfiltered, you may immediately notice a dazzle effect, or a glare the way you would from any bright object, but that doesn’t necessarily mean your retina is damaged. According to Chou, symptoms generally begin occurring 12 hours after viewing the eclipse, when people wake up in the morning and notice their vision has been altered.

“They can&rsquot see faces in the mirror, they can&rsquot read the newspaper or the smartphone display, they&rsquore having trouble looking at road signs, and basically they&rsquove got this center spot in their vision that is intensely blurred,” Chou said.

There are no remedies to effectively mitigate the injury, said Chou, aside from waiting and seeing if the patient regains vision. This does happen, but not until at least three months after the injury.


Safe Viewing

It is never safe to look directly at the Sun! Even for an instant. Do not look at the Sun through binoculars, a camera, or a telescope without purpose-built filters. Use your eclipse viewers, welders glasses that are rated at least #14, or project the image using a pinhole camera, for example.

Eclipse viewing glasses look like this, and are safe to use when viewing the Sun. While looking away from the Sun, put the glasses on, then look at the Sun through your glasses. Don&rsquot remove the glasses until you are looking in a direction away from the Sun.

Are my glasses safe?

If the manufacturer went through the ISO certification process, the glasses would be stamped with something like 'ISO 12312-2 certified'. If they are not, they didn't go through the certification process, and they may or may not be safe as they haven't been tested. Unfortunately, some vendors have stamped their glasses with this even though they haven't been certified.

If you know what vendor you purchased them from, you could try look them up, the American Astronomical Society (AAS) has a list of vendors that are carefully checked.

The AAS page also talks in details about the safety, and while it is impossible without lab equipment to do a rigorous check, there are a few things you can do to check if they are NOT safe (this could be the case also if there is a scratch in an otherwise good pair of eclipse viewers):

You shouldn't be able to see anything through a safe solar filter except the Sun itself or something comparably bright, such as the Sun reflected in a mirror, a sunglint off shiny metal, the hot filament of an unfrosted incandescent light bulb, a bright halogen light bulb, a bright-white LED bulb (including the flashlight on your smartphone), a bare compact fluorescent (CFL) bulb, or an arc-welding torch. All such sources (except perhaps the welding torch) should appear quite dim through a solar viewer. If you can see shaded lamps or other common household light fixtures (not bare bulbs) of more ordinary brightness through your eclipse glasses or handheld viewer, and you're not sure the product came from a reputable vendor, it's no good. Safe solar filters produce a view of the Sun that is comfortably bright (like the full Moon), in focus, and surrounded by dark sky. If you glance at the Sun through your solar filter and find it uncomfortably bright, out of focus, and/or surrounded by a bright haze, it's no good.

A pinhole camera is a cheap and simple way to safely view the Sun. Here are some instructions:

Department of Physics and Astronomy
The University of New Mexico
MSC07 4220
210 Yale NE
Albuquerque, NM 87106
505-277-2616
505-277-1520 fax


When the eclipse appears over Austin, DO NOT STARE AT IT

Staring at the sun is always a bad idea. It&rsquos a bad idea even when the moon slides in front of the sun and blocks out most of the sun&rsquos rays, as will happen on Monday for a little over two-and-a-half minutes.

Basically, looking at the sun can give your eyeball a sunburn. Robert Rosa, an ophthalmologist at the Texas A&M University Health Science Center College of Medicine, explains in more detail:

Q: Why shouldn&rsquot you look into a solar eclipse?

A: Staring at the sun for even a short time without wearing the right eye protection can damage the macula, which is responsible for our fine vision.

MAKE YOUR PLANS: Where to watch the solar eclipse in Central Texas

Q: Is this painful as it&rsquos happening?

Q: Is there a way to view a solar eclipse (without damaging my eyes)?

A: The American Academy of Ophthalmology website suggests that, "There is only one safe way to look directly at the sun," whether during an eclipse or not: through special-purpose solar filters. These solar filters are used in "eclipse glasses" or in hand-held solar viewers. They must meet a very specific worldwide standard known as ISO 12312-2 &hellip

Q: So I can&rsquot just use my sunglasses? They&rsquore really awesome.

A: Ordinary sunglasses, even very dark ones, or homemade filters are not safe for looking at the sun. (Emphasis is Rosa&rsquos.)

Q: What if I accidentally glance at the sun? Will I be blinded?

A: Most people may get a brief glimpse of the sun inadvertently without any injury. Prolonged observation with eye fixation on the sun causes the most severe retinal damage.

Q: If I&rsquom wearing the ISO 12312-2 glasses, can I look through a camera or my telescope?

A: Never look at the uneclipsed or partially eclipsed sun through an unfiltered camera, telescope, binoculars or other similar devices. This is important even if you are wearing eclipse glasses or holding a solar viewer at the same time.

RELATED: Man who lost vision after staring at eclipse issues warning to sky watchers

A: The only time that you can look at the sun without a solar viewer is during a total eclipse. When the moon completely covers the sun&rsquos bright face and it suddenly gets dark, you can remove your solar filter to watch this unique experience. Then, as soon as the bright sun begins to reappear very slightly, immediately use your solar viewer again to watch the remaining partial phase of the eclipse.

*Author&rsquos note: Despite what you might have heard, the Monday eclipse will not be a total eclipse in Austin. Central Texas is not in the "path of totality," or places where the eclipse will be total. We will see only a partial eclipse, so don&rsquot get your hopes up. As writer Annie Dillard once wrote: "Seeing a partial eclipse bears the same relation to seeing a total eclipse as kissing a man does to marrying him."

Also, because it&rsquos a partial eclipse here, there is no time during which you can safely remove your eclipse glasses in Central Texas. Don&rsquot do it, people!


In summer, of course, since we're closer to the sun. [Note: It is actually hotter in the summer because the Earth's axis is tilted] But there are different ways you can get damage from the sun in your eyes. If you are outdoors a lot you can get a growth on the surface of your eye, called pterygium. It's found very commonly in people who live or grew up in equatorial regions, and a lot of surfers get it because the water reflects UV into eyes [the condition is also called Surfer's Eye]. If very severe, it can start to obscure your vision and cause irritation from time to time. That can be surgically removed, however.

Chronic sun exposure can also contribute to formation of cataracts and macular degeneration. So, wear sunglasses as often as it makes sense to.


References

American Conference of Governmental Industrial Hygienists, "Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices," ACGIH, Cincinnati, 1996, p.100.

Chou, B. R., "Safe Solar Filters," Sky and Telescope , August 1981, p. 119.

Chou, B. R., "Eye safety during solar eclipses - myths and realities," in Z. Madourian & M. Stavinschi (eds.) Theoretical and Observational Problems Related to Solar Eclipses, Proceedings of a NATO Advanced Research Workshop . Kluwer Academic Publishers, Dordrecht, 1996 (in press).

Chou, B. R. and Krailo M. D., "Eye injuries in Canada following the total solar eclipse of 26 February 1979," Can. J. Optometry , 1981, 43(1):40.

Del Priore, L. V., "Eye damage from a solar eclipse" in M. Littman and K. Willcox, Totality: Eclipses of the Sun , University of Hawaii Press, Honolulu, 1991, p. 130.

Marsh, J. C. D., "Observing the Sun in Safety," J. Brit. Ast. Assoc. , 1982, 92, 6.

Pasachoff, J. M., and Covington, M., Cambridge Guide to Eclipse Photography , Cambridge University Press, Cambridge and New York, 1993.

Pasachoff, J. M., "Solar Eclipses and Public Education," International Astronomical Union Colloquium #162: New Trends in Teaching Astronomy , D. McNally, ed., London 1997, in press.

Penner, R. and McNair, J. N., "Eclipse blindness - Report of an epidemic in the military population of Hawaii," Am. J. Ophthalmology , 1966, 61:1452.

Pitts D. G., "Ocular effects of radiant energy," in D. G. Pitts & R. N. Kleinstein (eds.) Environmental Vision: Interactions of the Eye, Vision and the Environment , Butterworth-Heinemann, Toronto, 1993, p. 151.

Reynolds, M. D. and Sweetsir, R. A., Observe Eclipses , Astronomical League, Washington, DC, 1995.

Sherrod, P. C., A Complete Manual of Amateur Astronomy , Prentice-Hall, 1981.


Keep Safe!

    without protective eye gear. Even sunglasses cannot protect your eyes from the damage the Sun's rays can do to them.
  • Always keep your back towards the Sun while looking at a pinhole projection.
  • Do not look at the Sun through the pinhole, binoculars or telescope.

Next Partial Lunar Eclipse

Eclipse Lookup

Protect Your Eyes

Solar Eclipses

PDF Guide: How to View a Solar Eclipse

Sunglasses don't work! Print our guide to protecting your eyes to safely see a solar eclipse.


NASA Advisory for Safely Viewing the August 21 Total Solar Eclipse

Looking directly at the sun is unsafe. Even during the upcoming solar eclipse, the only safe way to look directly at the eclipsed sun is through special-purpose solar filters, such as “eclipse glasses” or other equipment that is outfitted for safely viewing the Sun. Regular sunglasses, even very dark ones, are not safe for looking at the Sun – they simply let in too much dangerous sunlight.

To make sure you are buying solar safe equipment you can go to the American Astronomical Society’s Reputable Vendors of Solar Filters & Viewers page for a list of manufacturers and authorized dealers of eclipse glasses and handheld solar viewers verified to be compliant with the ISO 12312-2 international safety standard for such products.

NASA has released an advisory on how to safely view the solar eclipse. Here are specific recommendations as provided by NASA:

– Always inspect your solar filter before use if scratched or damaged, discard it. Read and follow any instructions printed on or packaged with the filter.

– Always supervise children using solar filters.

– Stand still and cover your eyes with your eclipse glasses or solar viewer before looking up at the bright sun. After looking at the sun, turn away and remove your filter — do not remove it while looking at the sun.

– Do not look at the uneclipsed or partially eclipsed sun through an unfiltered camera, telescope, binoculars, or other optical device.

– Similarly, do not look at the sun through a camera, a telescope, binoculars, or any other optical device while using your eclipse glasses or hand-held solar viewer — the concentrated solar rays will damage the filter and enter your eye(s), causing serious injury.

– Seek expert advice from an astronomer before using a solar filter with a camera, a telescope, binoculars, or any other optical device. Note that solar filters must be attached to the front of any telescope, binoculars, camera lens, or other optics.

– If you are within the path of totality, you can remove your solar filter only when the moon completely covers the sun’s bright face and it suddenly gets quite dark. Experience totality, then, as soon as the bright sun begins to reappear, replace your solar viewer to look at the remaining partial phases.

– Outside the path of totality, you must always use a safe solar filter to view the sun directly.

– If your eclipse glasses or viewers are compliant with the ISO 12312-2 safety standard, you may look at the uneclipsed or partially eclipsed Sun through them for as long as you wish. Furthermore, if the filters aren’t scratched, punctured, or torn, you may reuse them indefinitely. Some glasses/viewers are printed with warnings stating that you shouldn’t look through them for more than 3 minutes at a time and that you should discard them if they are more than 3 years old. Such warnings are outdated and do not apply to eclipse viewers compliant with the ISO 12312-2 standard adopted in 2015.

– An alternative method for safe viewing of the partially eclipsed sun is pinhole projection. For example, cross the outstretched, slightly open fingers of one hand over the outstretched, slightly open fingers of the other, creating a waffle pattern. With your back to the sun, look at your hands’ shadow on the ground. The little spaces between your fingers will project a grid of small images on the ground, showing the sun as a crescent during the partial phases of the eclipse. Or just look at the shadow of a leafy tree during the partial eclipse you’ll see the ground dappled with crescent Suns projected by the tiny spaces between the leaves.

NASA also provides much more information on the Great American Solar Eclipse on its 2017 eclipse website.

The Astronomy Technology Today editorial staff would like to take this opportunity to remind you of the availability of our Solar eclipse equipment guide – The Definitive Equipment Guide to the 2017 Solar Eclipse. Our goal with the 40 page publication is to provide an easy-to-consume introduction to the technological options for viewing and imaging the Great Solar Eclipse. We cover the gamut of options available including building your own solar viewer, solar glasses, smart phones, DSLR cameras, using astronomy telescopes, solar telescopes, using binoculars, solar filters (including a DYI filter option), CCD astro cameras, astro video cameras, webcams and much more. You can view the guide on our website here – its free and there is no requirement to sign up to read the guide.