Everything you need to know to view solar eclipses safely

Viewing a solar eclipse can be an awe-inspiring experience as the moon passes between the earth and sun, temporarily blocking out sunlight. However, taking the proper precautions is crucial, as viewing an eclipse without protection can cause permanent eye damage and even blindness.

This comprehensive guide will provide you with everything you need to know to view solar eclipses safely and enjoy these celestial events worry-free. We'll cover choosing proper eye protection, techniques for direct and indirect viewing, how to photograph eclipses, and more.

Choosing Safe Solar Filters and Eclipse Glasses

The only way to view a solar eclipse directly with unassisted eyes is by using special-purpose solar filters or handheld solar viewers. Known as "eclipse glasses" or "solar eclipse glasses", these specially designed glasses block harmful ultraviolet and infrared radiation and reduce visible sunlight to safe levels.

Regular sunglasses, even very dark ones, are not safe for looking directly at the sun. They transmit thousands of times too much sunlight.

When selecting eclipse glasses, proper certification is crucial. Acceptable glasses will be marked with a ISO 12312-2 international safety standard, which indicates they filter out sufficient sunlight for direct solar viewing. Some common manufacturers of ISO-approved eclipse glasses include American Paper Optics, Rainbow Symphony, Celestron, and Thousand Oaks Optical.

Homemade filters or uncertified glasses should never be used, even if they seem adequately dark. The safest route is to only use eclipse glasses that come from a reputable manufacturer with the proper ISO rating. Checking for certification is essential.

Techniques for Safe Direct Viewing

With proper solar filters or eclipse glasses, you can look directly at the sun during a solar eclipse. Here are some tips for safe solar viewing:

• Inspect your filters before use. Check for scratches, punctures or loose glass that could compromise their filtering ability. Do not use damaged glasses.
• Supervise children using solar filters. Ensure glasses fit properly and aren't removed without your knowledge.
• Do not look at the sun through binoculars, telescopes, cameras or other optical devices unless they have certified solar filters installed over the optics. The concentrated solar rays can damage eyes and equipment.
• Stand still and cover your eyes with the glasses before looking up at the sun. Then move your head, not the glasses.
• Look only at the sun. Do not try to look at the eclipsed sun's surroundings, as the sun's rays can still damage eyes when filtered incorrectly.
• Stop looking directly as totality ends. Make sure to put the solar filters back on after the moon starts revealing the sun's surface, when harmful rays begin being emitted again.

Following these safe solar viewing guidelines will allow you to experience the eclipse's stunning partial phases worry-free. Never remove the solar filters while the sun's surface is exposed.

Techniques for Indirect Viewing

Besides eclipse glasses, there are alternative indirect techniques that can let you safely view the partial phases of a solar eclipse without looking directly at the sun:

• Pinhole projection. Poke a small hole in a piece of cardboard, and project the eclipse's image onto a shaded surface like the ground or wall. This simple DIY method provides a safely indirect view.
• Reflection. Fill a large bowl with water and float a piece of light-colored cardboard on top. Facing away from the sun, look down at the water where sunlight will be refracted onto the cardboard, producing the eclipsed sun's reflection.
• Mirror projection. Position a small or flat mirror outdoors so it reflects a spot of sunlight onto a shaded viewing surface. Slowly rotate the mirror to follow the sun's movement and watch the reflected image.
• Live webcast. Watch footage streamed online from observatories and eclipse teams. This lets you see the eclipse in real-time without any eye hazard.

These indirect techniques can engage kids and allow broader viewing of the partial eclipse phases leading up to and following totality, when using eclipse glasses becomes essential.

Photographing Solar Eclipses Safely

Capturing photos or video of a solar eclipse provides lasting mementos, but special methods are required to image the sun safely:

• Install a solar filter on your camera, telescope, monocular or binoculars. Solar filters that fit over optics are available from astronomy retailers. Ensure they are certified and completely cover the front of the instrument.
• Use a solar filter on the END of your lens for DSLR photography. Attach it at the end of the scope farthest from the camera body, not at the front near the attachment ring.
• Use manual exposure settings on DSLRs. The decreasing light during the eclipse can fool your camera's auto exposure. Set adjustments manually.
• Bracket exposures. Take multiple shots at different exposures to ensure you capture details of the corona and solar features.
• Remove solar filters for totality. When the moon entirely blocks the sun's face, it's safe to image totality without filters and capture the fuller brightness of the corona. Just be sure to reattach them before totality ends!
• Consider using a solar telescope with a camera mount. They provide optimal stability and high focal length magnification for photographing a magnified eclipse.

Safety Tips for Eclipse Chasers

For people traveling to observe total solar eclipses at their narrow paths of totality, coordinating safe viewing takes extra preparation:

• Research the eclipse's path. Make sure your location lies in the path of totality, where the moon will entirely block the sun's face. Otherwise only partial viewing is possible, requiring filters.
• Check weather forecasts. Be prepared to adjust plans if clouds threaten to obscure the eclipse. Even high thin clouds can dull viewing, so have backups in mind.
• Arrive early at viewing sites. To secure good less-crowded spots, arrive the day before. Morning traffic and limited parking will be challenges during the eclipse.
• Bring plenty of eclipse glasses. Don't assume glasses will be available onsite. Vendors often sell out fast. Bring enough for your whole group.
• Use indirect viewing around sunrise/sunset. Just before and after totality as the sun nears the horizon, techniques like shadow projection are safer than solar filters.
• Practice manual camera settings beforehand. Test your equipment, settings and exposures required to photograph the partial phases and totality well before the eclipse.

By keeping these tips in mind, eclipse chasers can experience the awe of totality safely. Never rely on makeshift filters, and follow proper eye protection methods for direct and indirect viewing when the sun's surface is visible.

Dangers of Viewing Eclipses without Proper Eye Protection

Viewing the sun without certified solar filters as sunlight reappears from behind the moon can easily cause serious and permanent eye damage. The retina's exposure can lead to:

• Solar retinopathy - destruction of retinal tissues from solar radiation and infrared heat. Can cause partial vision impairment.
• Solar maculopathy - burning of the macula, the part of the retina responsible for sharp central vision. Often causes solar blind spots.
• Solar chorioretinitis - inflammation of both retinal and choroidal tissues, often severely impairing vision.
• Photokeratitis - a sunburn of the cornea and retina from UV exposure. Causes painful eye inflammation.

Even brief accidental views of the partially eclipsed sun's rays are hazardous. Symptoms like blurred vision, central dark spots and distorted vision can begin hours after the exposure. In severe cases, permanent blindness results. Safe solar filters are a must for eclipse viewing.

With right knowledge equipped you are prepared for the upcoming solar eclipses, share this with friends