Q&A: Adler Planetarium offers tips for safe eclipse watching

In just under two weeks, the suburbs, along with most of the United States, will be treated to a rare astronomical experience that has awed and fascinated people since the beginning of human history — a solar eclipse.

It’s a naturally exciting phenomenon, but one that requires some preparation and caution to experience fully. We posed questions to the folks at the Adler Planetarium in Chicago seeking tips on photographing and viewing the eclipse. Director of Public Observing Michelle Nichols gave these tips for a safe and enjoyable experience:

In order to photograph the eclipse, what type of filter should be used to avoid damage to the camera sensor and the photographer’s eyes? Groups dedicated to eclipse observation state that an ISO 12312-2 rated filter or plastic sheet should be used.

The American Astronomical Society has great information about how to safely photograph a solar eclipse: https://eclipse.aas.org/imaging-video/images-videos. It isn't enough to just look for an ISO 12312-2 certification for a solar filter, because that certification listing can be counterfeit. The AAS website has a vetted list of suppliers of safe solar filters that are specifically designed for cameras, telescopes and binoculars. Go to this page & scroll down for the list: https://eclipse.aas.org/eye-safety/viewers-filters. [Side note: Nichols urged would-be photographers to act quickly to order the filter to have a better chance of receiving it in time.]

What precautions/equipment should people use to visually observe the eclipse?

Taking the wording directly from the AAS eclipse website: “The only safe way to look directly at the ‘uneclipsed’ or partially eclipsed Sun is through special-purpose solar filters, such as “eclipse glasses” or handheld solar viewers. Ordinary sunglasses, even very dark ones, are not safe for looking at the Sun; they transmit far more sunlight than is safe for our eyes. See [their] Suppliers of Safe Solar Viewers & Filters page for sources of solar viewers verified to be compliant with the transmittance requirements of the ISO 12312-2 international safety standard.”

There is more eye safety information available on the page where the quoted text above comes from, as well: https://eclipse.aas.org/eye-safety

There are also ways to indirectly view images of the partially eclipsed Sun. Details on how to make pinhole projectors are also on the AAS site: https://eclipse.aas.org/eye-safety/projection

What is the span of the geographic area from which the eclipse can be observed? Does the planetarium expect people from other areas of the U.S. or even worldwide to observe the eclipse at Adler?

The entire lower-48 United States plus Hawaii plus a small part of Alaska will be able to view the partial solar eclipse (also including Mexico, Canada, countries in Central America, several countries in the Caribbean, and a few other locations). The total solar eclipse will be visible in a narrow path running up from Texas, through southern Illinois, and on to the northeast. The Time and Date website has a useful clickable map for what to expect & where: https://www.timeanddate.com/eclipse/map/2024-april-8.

We do not know for sure if people from other areas will be observing the eclipse from the Adler. If visitors or tourists are in town and not planning to travel to a location within the path of totality, they might come and view it with us.

What is the time span for the eclipse, and when can we expect the next one?

From the Adler's location, about 94% of the Sun will be covered by the Moon at the eclipse's maximum extent (not totality, in other words). The eclipse will last at the Adler's location from 12:51 p.m. CT to 3:22 p.m. CT. The visibility of the eclipse will be weather- and cloud-dependent. How long the eclipse lasts is also location-dependent, as is the amount of the Sun that will be covered by the Moon.

While a solar eclipse happens on average on Earth about twice a year, a single location may see all, some, one or even none of the solar eclipses that occur in a given year.