Staring at the Sun

28 June, 2009

Moon takes a bite of the Sun.
Moon takes a bite of the Sun.
Source: NASA

Question: If we are unable to see the Sun by looking directly at it, is it ever safe to look at it through a telescope? Are there any other ways to look at the Sun?

Answer: It is only safe to view the Sun directly through a telescope that is fitted with a special filter. Alternatively an image of the Sun can be produced either using a telescope or with an easy-to-make pinhole camera.

The most common filter used for solar viewing is the H-alpha (hydrogen-alpha) filter. Sunlight is made up of all the colours of the rainbow and this filter works by blocking most of the sun's light and allowing only a small amount of red light to pass through. Not only is the intensity of the Sun reduced but harmful UV and infrared light is also removed to fully protect the observer's eyes. Spectacular views of prominences (loops emanating from the Sun's surface) and sunspots are then possible. 

In the absence of a filter, you can use a telescope to project an image of the Sun onto another surface, such as a piece of cardboard. It is important never to look directly through the telescope or its finder scope, but by projecting the image of the Sun we can see it safely. It is important to make sure that the telescope is never left unattended while using this method.

The simplest way of safely viewing the Sun is to create a pinhole camera. This is easily done by taking a piece of cardboard and using a pin to create a small hole. With your back towards the Sun, hold the cardboard so that light passes through the hole onto a wall or other flat surface. You should then see an image of the Sun on that surface. Since this method doesn't involve a telescope, the image will be small and faint but it is great for watching the changing shape of the Sun during an eclipse.
A solar eclipse occurs when the Moon's shadow partly or fully covers the Sun. During a total solar eclipse, the Sun’s faint corona or outer atmosphere can be seen. Each year or so, somewhere in the world will experience a total solar eclipse. In 2009, one can be seen across India and China on 22 July. The next solar eclipse to be visible from Australia will occur on 14 November 2012. Totality will be visible from Cairns, while the rest of Australia will see a partial eclipse.

As a part of its celebration of the International Year of Astronomy, at certain times throughout the year Scienceworks will be conducting daytime astronomy sessions. These allow visitors to look safely at the Sun and enjoy the spectacular views provided by our very own star. Contact Scienceworks on 9392 4800 to find out when the next session will be held.

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