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Important warning about solar observations

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Never look directly at the sun.
Photo: Espace pour la vie (Planétarium de Montréal)

Protect your eyes!

Never look directly at the Sun. Always use a proper solar filter. Only the following filters are recommended:

  • filters specifically designed and approved for solar observation, available at astronomy stores;
  • specially designed "eclipse goggles" or "viewers" (Quebec's eye care professionals will offer them for free on August 21 at the Rio Tinto Alcan Planetarium);
  • #14 welder's glass (do not use a lower shade!), available at some hardware or welding supplies stores.

Look for filters that meet the requirements for ISO Standard 12312-2:2015

The Sun's intense radiation (visible light, ultraviolet and infrared) always presents a serious danger to the eye, especially to the central part of the retina known as the macula. The highly sensitive cells in this area can easily be burned since they absorb a maximum quantity of solar radiation which is then converted to heat. Retinal burns do not produce pain so there is no warning, and once damaged, these cells never regenerate. This page shows examples of retinal damage caused by observing the Sun without adequate eye protection.

Adequate solar filters must reduce the Sun’s infrared and ultraviolet radiation to within accepted safety thresholds, and they should allow no more than 0.001% of the Sun’s visible light to pass (equivalent to an optical density of 5). While some filters or “systems” appear to cut visible light to tolerable levels, they allow nearly all the invisible but dangerous infrared and ultraviolet radiation to pass through!

Do not use the following:

  • sunglasses (even expensive ones);
  • color negative film exposed to light and developed;
  • slide film unexposed to light and developed;
  • compact discs (CDs);
  • glass plates covered with soot;
  • crossed polarizing filters;
  • color acetates;
  • all other filters not specifically designed for solar observing.

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