Events such as solar eclipses and transits are exciting to watch, but you must ensure that you use the safest methods of viewing them.
Never look directly at the Sun.
Light from the Sun contains ultraviolet light and other dangerous forms of radiation. If these rays enter the eye, they can burn the retina and cause permanent eye damage.
You will not feel the damage being done, but it cannot be repaired.
The best method of viewing the Sun is to visit your local observatory, planetarium or local amateur astronomical society, which is likely to be running public viewing sessions. Some websites provide streaming images of the Sun on the Internet.
Pinhole viewer
The pinhole viewer is the simplest and safest way to view the Sun. Take a piece of card and use a pin to pierce a small hole.
Facing away from the Sun hold the card up so that light passes through the hole on to a wall or other flat surface. An image of the Sun should be visible. You can use this method to see the changing shape of a partial solar eclipse.
Alternatives to this method include using a square of aluminium foil stuck to a cardboard frame (to produce a smaller, more uniform hole), a kitchen colander (to produce multiple images of the Sun), or looking at the shadow of tree on the ground.
Although this method is the safest, it does have the disadvantage of producing a faint, small image.
Projection method
The projection method of viewing the Sun is regarded as the safest method of observing the Sun.
Viewing a projected image of the Sun is safe, but looking through the telescope will cause almost instant blindness. Do not use the binoculars, telescope or its finder scope to look directly at the Sun.
Never leave the binoculars or telescope unattended and ensure that children are supervised at all times. If you are using a telescope, cover both ends of the finder scope.
Further instructions on how to contruct a solar viewer using the projection method are provided in the 'Build a solar viewer' activity.
Viewing a total solar eclipse
You should never look directly at the Sun during a partial eclipse, or the partial phase of a total solar eclipse.
Even when the Moon covers 99.9 percent of the Sun, there is still enough light and radiation to damage your eyes.
Totality, when the Moon completely cover the Sun, is the only safe time to view a solar eclipse without filters. As totality ends and the Sun reappears you must immediately look away from the Sun.
Solar glasses
Solar glasses, are sold by some telescope shops to allow you to view the Sun directly. While many people believe that properly constructed solar viewers are safe, there are no Australian Standards for eclipse viewers and their safety is unproven.
CSIRO does not endorse the use of these solar viewers. People who elect to use them do so at their own risk.
Solar viewers need to block out harmful ultraviolet and infrared radiation. There are a range of solar filters that claim to have passed the Australian/New Zealand safety standards 1338.2 and 1338.3. These standards have been developed for welder's masks and and are not designed for the purpose of testing solar filters.
Associate Professor Dr Ralph Chou, School of Optometry at the University of Waterloo, Canada, has further information on this topic on the NASA eclipse website.
Definitely not suitable
Sunglasses are definitely not suitable for viewing the Sun. They still allow harmful UV light to reach your eyes. Do not use them for viewing either the Sun or the transit of Venus.
The following are considered unsafe and therefore not suitable for looking at the Sun:
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sunglasses
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space blankets
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CDs
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exposed colour film
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neutral density filters
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polarising filters
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smoked glass.
Also, you should not use solar viewing eyepieces in a telescope. The only safe filters for telescopes and binoculars are attached to the objective lens (the end pointed at the Sun), not the eyepiece.
Find out more about safe viewing at NASA's Eye Safety during an Eclipse [external link].
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