As most of Asia prepares to view the longest total solar eclipse of the 21st century, the Bishop Museum has a list of safe and unsafe viewing techniques to protect our eyes.

In Hawaii, the moon will start to take a small bite out of the sun at 5:20 p.m. today, according to the Bishop Museum. By 6:14 p.m., roughly an hour before sunset, the eclipse will be over. These times are about the same for all the main Hawaiian Islands: In Hilo, the eclipse will start at 5:24 p.m. and end at 6:15 p.m.; in Lihue, it will start at 5:18 p.m. and end by 6:14; in Lahaina, start time is 5:22 p.m. and end time 6:14 p.m.

UNSAFE AND SAFE ECLIPSE VIEWING TECHNIQUES

Warning: Improper viewing of a partial solar eclipse can cause severe and permanent eye damage.

The retina of your eye cannot feel pain, so you will not notice damage being done to your vision until it is too late. “Homegrown” filters may seem to provide an image that does not look too bright in visible light and therefore are tempting to use. However, almost all of these homegrown filters allow too much ultraviolet and infrared light to pass through. Too much infrared light will act like an infrared heat lamp and can “cook” the retina of your inner eye quickly. Too much ultraviolet light and the cornea of your eye can cloud over.

UNSAFE VIEWING TECHNIQUES:

UNSAFE: Smoked glass, no matter how dark.

UNSAFE: Exposed color film, no matter how many layers

UNSAFE: Multiple pairs of sunglasses.

UNSAFE: Looking at the sun with the naked eye, even through layers of clouds.

UNSAFE: Looking through the viewfinder of a camera that does not have a special reflective filter.

UNSAFE: Looking through any telescope or binoculars without professional solar filters on the front of the optics. (Note: many small telescopes are sold with solar filters that screw into the eyepiece at the back of the camera. These are potentially hazardous because the heat build-up inside the telescope can cause the filter to crack, resulting in the full, unfiltered light of the sun reaching your eye. This can cause instant eye damage.)

There are several safe viewing techniques that allow anyone to experience the excitement of watching the sun as it is eclipsed by the moon. These techniques can also be used on any clear day to see sunspots on the sun.

These safe viewing methods include direct viewing through special solar filters and indirect solar projection.

SAFE SOLAR FILTER TECHNIQUES:

SAFE: Inexpensive hand-held solar viewing filters (“sun peeps”) are commercially available. These filters allow a safe amount of visible light to pass through, while reflecting back the dangerous ultraviolet and infrared rays.

SAFE: Special solar filters that mount on the front of a telescope are available from astronomy specialty stores. However, these do cost several hundred dollars on up.

SAFE INDIRECT PROJECTION TECHNIQUES:

NOTE: Projection techniques focus an image of the sun onto a piece of white paper, where it can be safely viewed by anyone nearby.

Using these techniques, you will be looking down at a piece of paper, not looking directly at the sun.

SAFE: The spot mirror projection technique. Cover a small mirror (a plain hand mirror works fine) with a sheet of paper that has a dime-sized hole cut in the center. Tape the sheet of paper to the mirror.

Bounce the image of the sun onto a sheet of white paper 30 feet to 40 feet away. The darker the screen area is, the better the image shows up. Here, we’ve found that a tipped-over garbage can make a great shady area to project the image into.

If you are using a mirror with a handle, you can stick the mirror in a bucket of sand to hold it, rather than having to hand-hold the mirror yourself.

SAFE: Another safe technique, if carefully monitored by an adult at all times, is binocular projection. Into a sheet of cardboard, cut a single round hole just big enough to fit over one of the large lenses of a pair of binoculars. Put the binoculars with this cardboard mask on a tripod or prop them against something steady like a chair. Place a sheet of white paper to act as a projection screen 2 feet to 3 feet behind the binoculars in the shade of the cardboard mask. WITHOUT LOOKING THROUGH THE BINOCULARS, point the big end of the binoculars at the sun and move them around a bit into a flash of white light can be seen on the paper. Once you get an image of the sun on the paper move the paper in or out and adjust the focus knob on the binoculars to produce a clear and sharp image of the sun.
DO NOT PUT YOUR EYE UP TO THE BINOCULARS AND KEEP OTHERS AWAY ALSO. IF ANYONE LOOKS AT BINOCULARS AIMED AT THE SUN, INSTANT EYE DAMAGE WILL OCCUR.

SAFE: Telescope projection. Follow the same instructions as provided for binocular projection above.
THE SAME WARNINGS APPLY: NEVER LOOK THROUGH A TELESCOPE WHEN IT IS POINTED AT THE SUN. DON’T FORGET TO LEAVE THE CAP ON, OR COVER, THE SMALL VIEWFINDER (SPOTTING SCOPE) LOCATED ON THE SIDE OF THE MAIN TELESCOPE. LOOKING THROUGH THE SMALL TELESCOPE WILL ALSO CAUSE EYE DAMAGE.