Eight percent. That is roughly how much of the solar disk remains uncovered in Milan at maximum eclipse on August 12, 2026. Safe solar eclipse glasses are still necessary because the exposed crescent remains unsafe to view without a proper filter.
How much of the Sun has to vanish behind the Moon before it becomes safe to look at?
For Italy and most of Europe, the answer is all of it, and that never happens there during this eclipse. A proper solar filter remains necessary throughout the event. We will show you how to verify it, use it with prescription glasses, handle cameras and telescopes, and recognize symptoms that need an ophthalmologist.
The short answer: Use viewers from a traceable manufacturer whose products have been tested to ISO 12312-2 by a competent laboratory. Inspect them before use, put them on before looking up, and never place them behind magnifying optics or a camera lens.
August 12 over Europe
The August 12, 2026 eclipse crosses northern Russia, Greenland, Iceland, the North Atlantic, and northern Spain, with a small part of Portugal also inside the path of totality. The longest total phase lasts less than two and a half minutes. Most locations receive less than two minutes.
Italy sees a partial eclipse near sunset. In Milan, the eclipse begins at 7:27 p.m. local time and reaches about 92 percent coverage at 8:20 p.m.; sunset follows before the partial phase ends. Ventimiglia reaches about 94.8 percent, while parts of the northwestern Tyrrhenian coast and western Sardinia approach 90 percent. You need a clear west-northwestern horizon. For mainland Europe, this is the first total solar eclipse since 1999, although Italy remains outside totality.
The event is also listed in our 2026 astronomy events guide. That calendar tells you when to look; this page answers the harder safety question.
- 92 percent solar coverage in Milan at maximum eclipse
- 94.8 percent coverage near Ventimiglia
- Less than 2.5 minutes of totality at the global maximum
Sunglasses are not solar eclipse glasses
Ordinary sunglasses are designed for comfort in daylight, not for direct observation of the Sun. Eclipse viewers must suppress visible light by tens of thousands of times while also limiting ultraviolet and infrared transmission. Stacking several pairs of sunglasses does not turn them into a solar filter.
At a given solar altitude, an eclipse reduces the exposed area of the photosphere; it does not dim the surface brightness of the part that remains visible. Low altitude adds atmospheric attenuation, but it does not make direct, unfiltered viewing safe.
For direct solar observation, the relevant standard is ISO 12312-2. ISO 12312-1 applies to ordinary sunglasses.
Inside ISO 12312-2
ISO 12312-2 sets optical, mechanical, labeling, and user-information requirements for eclipse viewers. It was adopted in 2015 and affirmed in 2020. The standard is more demanding than a logo printed on cardboard.
Transmission and material quality
The maximum permitted luminous transmittance is 0.0032 percent, about one part in 31,000. If eight percent of the Sun remains exposed, a simple same-altitude comparison gives 0.08 divided by 0.000032, or about 2,500. That exposed crescent can deliver roughly 2,500 times the standard’s maximum whole-Sun visible-light transmission through a compliant filter.
Table 1 — Key requirements in ISO 12312-2:2015, as summarized by the American Astronomical Society Solar Eclipse Task Force
| Requirement | Limit | Why it matters |
|---|---|---|
| Visible light | 0.0032 percent maximum; lower bound near shade 15 | Keeps the disk comfortable and visible |
| Infrared | 3 percent maximum | Applies to unmagnified viewing |
| Ultraviolet | No higher than luminous transmission | Limits short-wave radiation |
| Uniformity | Within 10 percent | Avoids weak patches |
| Pinhole defects | 200 micrometers maximum within 5 millimeters | Rejects larger nearby flaws |
| Mounting | Covers both eyes and resists handling | Prevents filter displacement |
| Labeling | Maker, warning, storage, and discard advice | Allows traceability and safe use |
The looser infrared limit is deliberate. For unmagnified viewing, infrared reaching the retina is less effective at causing injury than ultraviolet or visible light. Put a lens in front of the filter and the exposure changes, which is why cameras and other magnifying optics require separate front-mounted filters.
The pinhole clause deserves attention. The standard permits no defect larger than 200 micrometers within 5 millimeters of another defect, a detail that does not appear in most sales copy. It also rejects bubbles, scratches, dull spots, and pitting that could impair the view. Tiny isolated points of light can be acceptable; tears, creases, peeling film, and clusters are not.
Labels, laboratories, and welding glass
ISO writes standards; it does not test or certify products. A manufacturer may print the standard number or an ISO logo on a viewer, but the claim is useful only when the product can be traced to a known maker and supported by testing from an ISO/IEC 17025-accredited laboratory or, in Europe, an appropriate notified body. From the frame alone, we cannot know whether that testing happened.
The American Astronomical Society reviews test reports and maintains a supplier list without charging manufacturers. Buy directly from a listed maker or one of its publicly identified authorized resellers; a familiar manufacturer name printed on an unknown product can be copied. The AAS specifically warns against buying whichever eclipse-glasses advertisement appears first in a search. Its list is a practical starting point, not a government guarantee.
A 2021 study by Ralph Chou, Stephen Dain, and Richard Fienberg tested 43 eclipse viewers; all passed the ultraviolet and infrared requirements, but only 18 fell within the visible-light range while 24 were borderline too light or too dark. A printed standard number cannot carry the whole argument.
Fixed-shade welding glass is a separate option. Shade 12 is the minimum generally recommended for direct solar viewing, while shades 13 and 14 are more comfortable for many people. Adjustable or auto-darkening welding helmets are unsuitable because their transmission can change.
Check the glasses before looking up
A safe viewer should survive six checks before it reaches your eyes.
- Trace the maker. Buy from a supplier whose manufacturer and test history can be checked.
- Read the frame. Look for ISO 12312-2, the manufacturer’s name and address, and clear instructions.
- Inspect the filter. Reject viewers with scratches, tears, punctures, loose film, peeling layers, or serious creases.
- Test indoors. You should see almost nothing except very bright lamps, and those should appear faint.
- Test outside. Turn away from the Sun, put the viewers on, then look briefly. The solar disk should appear comfortably dim and sharply defined.
- Check age and storage. Verified viewers less than ten years old can be reused when the filters are undamaged and the instructions do not set an earlier expiry date.
Put eclipse viewers over prescription glasses. Stand still. Cover your eyes before turning toward the Sun, and turn away before removing the viewer. Children need close supervision because a safe filter cannot compensate for taking it off at the wrong moment.
Reuse and storage
Store viewers flat, dry, and protected from abrasion. Do not use them after the filter has separated from the frame or developed damage. The old blanket rule that eclipse glasses expire after three years no longer applies to compliant, undamaged products unless the manufacturer says otherwise.
Cameras and magnifying optics
Never look through a camera or any magnifying instrument while wearing eclipse glasses. Concentrated sunlight can damage the filter and your eye. A purpose-made solar filter belongs over the front aperture, before light enters the optical system.
We are not giving a camera-exposure recipe here. Different optical systems and mounts need equipment-specific guidance, and experienced solar observers should check the setup before use.
Viewing time follows provenance
Verified, undamaged ISO-compliant viewers can be used continuously during the partial phase. On a separate page about judging viewer safety, the American Astronomical Society gives a cautious fallback when you are not completely confident: look for only two or three seconds, then wait about five minutes before looking again. Geopop repeats that cautious advice for Italian observers.
Those statements are not contradictory. One applies to a product with dependable provenance; the other reduces exposure when that confidence is missing. Rationing your glances is a poor way to manage doubt about a filter. If you cannot trace the viewer to a tested manufacturer, do not use it.
A family does not need one pair per person. The partial phase changes slowly, so two good pairs can serve a family of six better than six doubtful ones. Put them on before each glance and turn away before passing them to the next observer.
Projection avoids direct viewing
Pinhole projection costs nothing and lets you follow the partial eclipse with your back to the Sun. Cross the fingers of both hands to make a grid of small openings, hold up a kitchen colander, use a perforated spoon, or punch holes in a card. Each opening projects a small solar crescent onto the ground or another pale surface.
Tree leaves do the same job naturally. Gaps between leaves form thousands of pinhole images, so the ground can fill with crescents near maximum eclipse.
Never look through the hole; watch the projected image on the surface in front of you.
Solar retinopathy gives no warning
Solar retinal injury is painless while it happens because the retina has no pain receptors. Symptoms often appear four to six hours later and can take as long as twelve hours to become obvious.
Warning signs include blurred vision, a central blind spot, distorted straight lines, unusual light sensitivity, headache, or changes in color vision. Sore or watery eyes alone may reflect the bright outdoor environment rather than retinal injury, but any change in vision after solar viewing needs prompt assessment by an ophthalmologist.
Retinal scans after the 2017 eclipse showed crescent-shaped injuries that matched the exposed Sun. There is no established treatment for solar retinopathy. Some people recover over weeks or months; others keep a permanent central defect.
Watching the eclipse well
The Moon takes about an hour and ten minutes to move from first contact to maximum eclipse above Milan, then the Sun sets before the partial phase finishes.
Buy the filter before the last-minute rush, test it indoors, and check it again on eclipse day. The safety plan is simple enough to remember: trace the viewer, inspect it, cover your eyes before looking up, and keep all magnifying optics behind a front-mounted solar filter.
False astronomy stories ask you to fear an invented event. We examined one in our analysis of the Project Anchor gravity hoax. A real eclipse asks for the opposite response: respect a measurable hazard, use equipment that meets a testable standard, and then enjoy the sky without theatrics.
Eclipses arrive on schedules that generations of observers learned to predict through careful measurement. The August 12 event needs an open western horizon and one filter whose provenance you can trace. Keep asking what the evidence allows, and keep your eyesight for the next sky. FreeAstroScience will keep doing the same.
Never let your Mind sleep.
Gerd Dani
References & Sources
- Chou, B. R., Dain, S. J., and Fienberg, R. T. (2021). Physical and Visual Evaluation of Filters for Direct Observation of the Sun and the International Standard ISO 12312-2:2015. The Astronomical Journal, American Astronomical Society. Published August 13, 2021. DOI: 10.3847/1538-3881/ac013e. https://iopscience.iop.org/article/10.3847/1538-3881/ac013e
- International Organization for Standardization (2015). ISO 12312-2:2015, Eye and face protection — Sunglasses and related eyewear, Part 2: Filters for direct observation of the Sun. Published March 2015. https://www.iso.org/standard/59289.html
- Chou, B. R. (2023). Solar Eclipse Eye Safety. American Astronomical Society technical report. Published 2023. https://eclipse.aas.org/sites/eclipse.aas.org/files/AAS-Chou-Tech-Report-Solar-Eclipse-Eye-Safety-2023.pdf
- Thomas, V. (2026). Total Solar Eclipse on August 12, 2026. NASA Science. Updated June 5, 2026. https://science.nasa.gov/eclipses/future-eclipses/total-solar-eclipse-on-august-12-2026/
- American Astronomical Society Solar Eclipse Task Force (2026). How to View a Solar Eclipse Safely. Updated March 26, 2026. https://eclipse.aas.org/eye-safety
- American Astronomical Society Solar Eclipse Task Force (2026). How Can You Tell If Your Eclipse Glasses or Handheld Solar Viewers Are Safe? Accessed July 27, 2026. https://eclipse.aas.org/eye-safety/how-to-tell-if-viewers-are-safe
- Fienberg, R. T. (2026). About the ISO 12312-2 Standard for Solar Viewers. American Astronomical Society. Updated April 10, 2026. https://eclipse.aas.org/eye-safety/iso12312-2
- American Astronomical Society (2026). Suppliers of Safe Solar Viewers and Filters. Accessed July 27, 2026. https://eclipse.aas.org/eye-safety/viewers-filters
- American Academy of Ophthalmology (2024). Think You Hurt Your Eyes Watching the Eclipse? With Michelle Andreoli, MD. Accessed July 27, 2026. https://www.aao.org/eye-health/tips-prevention/think-you-hurt-your-eyes-watching-eclipse
- Brugnoni, S. (2026). Eclipse solare del 12 agosto 2026: come vederla in sicurezza dall’Italia. GeoPop, with Fabiana Andriolo, optician-optometrist and physicist. Published July 22, 2026. https://www.geopop.it/eclissi-solare-12-agosto-2026-italia-come-vedere-occhio-nudo-quali-occhiali-usare/
