A total solar eclipse is an awe-inspiring natural phenomenon. Many people would travel across the world just to see it progress slowly in a span of hours. But everyone is warned against the dangers of looking directly into the sun even when it would appear to be largely covered by the passing moon.
Professor B. Ralph Chou from the School of Optometry at the University of Waterloo has some eye safety tips for those eager to observe the extraordinary astronomical event that is the total solar eclipse.
Prof. Chou also offers some science lesson pointers to teachers and parents. The solar eclipse is a cosmic opportunity to pique children's mind to science wonders.
Total Solar Eclipse: Protect your eyes, get the right filters
"When a person looks repeatedly or for a long time at the Sun without proper protection for the eyes, this photochemical retinal damage may be accompanied by a thermal injury - the high level of visible and near-infrared radiation causes heating that literally cooks the exposed tissue," writes Prof. Chou.
To avoid "eclipse blindness" or retinal burns, view the sun with filters designed to protect the eyes. Prof. Chou recommends "shade number 14 welder's glass." You can buy this from welding supply stores.
Using floppy disks or ripped CDs for solar eclipse viewing? Uh-oh.
"The optical quality of the solar image formed by a floppy disk or CD is relatively poor compared to mylar or welder's glass," Prof. Chou warned.
The optometry expert further cautioned solar eclipse observers: "No filter should be used with an optical device (e.g. binoculars, telescope, camera) unless it has been specifically designed for that purpose and is mounted at the front end (i.e., end towards the Sun)."
"Unsafe filters include all color film, black-and-white film that contains no silver, photographic negatives with images on them (x-rays and snapshots), smoked glass, sunglasses (single or multiple pairs), photographic neutral density filters and polarizing filters. "
Nurturing Science Whiz: What parents and teachers can teach the kids during an eclipse
- Discuss the laws of motion and the mathematics of orbital motion, and how these are used in forecasting the occurrence of eclipses.
- Demonstrate the use of pinhole cameras and telescopes. Explain how the optics of these devices works.
- Discuss the changes in environmental light levels and relate this to radiometry and photometry.
- Associate behavior of plants and animals to the progress of an eclipse.