The sky — astronomy

How to Photograph a Solar Eclipse Safely

Look at and photograph a solar eclipse only through a filter that meets the ISO 12312-2 standard. The one exception is the brief phase of totality, when the Moon fully covers the Sun. A lunar eclipse is safe to watch and can be photographed with no special filter.

Safety comes first

The key rule is simple: during a solar eclipse, never look at the Sun with unprotected eyes, and never point a camera, binoculars or telescope at it without a proper solar filter. NASA guidance says the only time you can remove your filter is during totality, when the Moon completely covers the solar disk and the sky darkens. As soon as the first bright bead of sunlight returns, the filter goes back on.

Partial and annular eclipses have no totality phase. For those, a filter is needed the whole time.

What ISO 12312-2 means

ISO 12312-2 is the international standard for eyewear and filters made for safe direct viewing of the Sun. Look for it printed on the eclipse glasses or their packaging, along with the manufacturer's name and address. Inspect the glasses before use, and do not use them if they are scratched, punctured or damaged.

Ordinary sunglasses, even very dark ones, are not a substitute. Neither are X-ray film, old floppy disks, smoked glass, or several pairs of glasses stacked together.

A note about optics

Eclipse glasses are for your eyes, not for your lens. If you photograph with a camera, telescope or binoculars, the solar filter must be fitted over the front of the instrument before you aim it at the Sun. Never look through a viewfinder, binoculars or a telescope while wearing eclipse glasses: concentrated light can pass through the glasses and harm the eye. If you want to look through optics, use a filter made specifically for them. More on instruments is in binoculars or telescope.

Shooting with a phone

NASA advises placing a solar filter over the phone lens during the partial phases. You can also hold eclipse glasses steadily over the camera. Without a filter, sunlight can damage the sensor or simply give a poor image. Practical tips:

• Use a tripod or a support so the frame stays steady.
• Lock focus and exposure so they do not drift as the scene changes.
• A phone captures a small Sun. For a bigger disk you need a telephoto lens or telescope, always with a suitable solar filter.
• During totality you may remove the filter to capture the corona, but watch the clock and put the filter back before totality ends.

Shooting with a camera

For a DSLR or mirrorless camera, fit a solar filter over the front of the lens. A longer focal length gives a larger solar disk. Work with a tripod and a remote release or timer to avoid shake. Do not rely on the optical viewfinder of an SLR when shooting without a filter. Practice your exposure before eclipse day, for example on the ordinary Sun through the filter, because good settings depend on your gear and filter.

A safe alternative: projection

You can follow an eclipse without looking at the Sun at all. A small hole in a piece of cardboard lets light through and projects an image onto a white surface. You watch the projection with your back to the Sun. Gaps between tree leaves also cast many small crescent-shaped images on the ground during the partial phase.

Lunar eclipses: no risk

A lunar eclipse happens when the Moon passes into Earth's shadow. The Moon only reflects sunlight, so it is safe for the eyes: no glasses or filters are needed. You can watch with the naked eye, binoculars or a telescope.

To photograph it, use a tripod. During totality the Moon is much dimmer and often reddish, so exposures must be longer than for an ordinary full Moon. Start at a low ISO (sensor sensitivity) and raise it gradually, keeping an eye on blur caused by the Moon's apparent motion across the sky. Including a landscape in the frame can make a richer picture.

Preparation

• Check the time and location of the eclipse in a reliable source, such as NASA's eclipse pages.
• Test your equipment a few days ahead.
• Choose a place with a clear horizon and no obstructions.
• Enjoy the eclipse with your own eyes, not only through a screen. Sometimes the best photograph is a memory.

General help for watching the sky is in how to watch the sky.

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