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Your guide to the 2013 'Ring of Fire' eclipse

Get ready for the spectacular sight of an annular or partial solar eclipse over Australia this Friday morning. Ian Musgrave shares his tips on what you'll see where you live, and how to see it safely.

For the second time in six months, Australia will be treated to a solar eclipse on 10 May when a ring of fire will appear across a narrow band of locations in northern Australia.

From there it passes over Papua New Guinea, the Solomon Islands and Gilbert Islands before reaching its greatest point near Kiribati — its last point of landfall.

The rest of Australia, as well as the north island of New Zealand and Indonesia will see an excellent partial eclipse.

Unlike the total eclipse last November, the Moon will not cover the entire Sun. We are at a moment in Earth's history where the Moon is just far enough away from Earth that it is almost the same size as the Sun in the sky.

During a total eclipse, the moon goes directly in front of the Sun completely blocking it out treating us to a beautiful display of the solar corona.

However, the Moon is in an eliptical orbit around Earth. When the Moon is at its furthest from Earth it looks just a bit smaller than the Sun, so during an annular eclipse we see the silhouette of the Moon ringed by a sliver of Sun.

You must use safe viewing techniques at all times during annular and partial eclipses as the sun is never fully covered (see below for more details).

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Eclipse viewing in Australia

The track of the annular eclipse starts in remote Western Australia, passes over the Northern Territory deserts and then across far North Queensland.

Most of the places the eclipse track passes over are remote with difficult access and few, if any, amentities. As the dry season has just begun in northern Australia, viewing conditions for the annular eclipse should be good across most of the eclipse track. Still, given the difficulty of getting to these locations, you should carefully check the weather forecasts at the Bureau of Meteorology website before heading out.

The two places with the best access for this eclipse are Tennant creek in the Northern Territory and the Musgrave Roadhouse north of Laura in Queensland (which itself is 315 kilometres north of Cairns).

Both Tennant Creek and the Musgrave Roadhouse enjoy over four minutes of annular eclipse.

Those parts of Australia outside the annular eclipse path will have an excellent opportunity to see a good partial eclipse. North-eastern Australia sees a large amount of the Sun covered, but most of the rest of Australia will also see a decent 'bite' taken out of the Sun.

For a large part of Western Australia the eclipse begins before sunrise, but the sight of the partially eclipsed Sun rising above the horizon will be memorable.

The table below gives the times when the eclipse begins, is at maximum depth and ends for a number a major towns and cities including Tennant Creek and the Musgrave Roadhouse. Timing for other places will be similar to the city or town nearest to you.

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What to see

While as not as ethereally beautiful as the total solar eclipse, an annular solar eclipse is still spectacular.

If the sight of the thin rim of Sun around the Moon like a glittering golden ring is not enough, you will also see the beautiful Baily's beads — flashes of bright sunlight between lunar mountains and valleys.

Baily's beads are first seen just as the Moon fully enters the solar disk, when the edge of the Moon begins to move away from the edge of the Sun (technically second contact).

Then they appear again as the Moon leaves the solar disk, when the edge of the Moon just touches the edge of the Sun.

The day will not become twilight, but there will be a noticeable darkening and cooling during the annular eclipse. Venus may be able to be glimpsed close to the horizon below the Sun, but no other stars or planets will be visible.

But, as the Sun is never completely covered, at all times you must use safe solar viewing techniques, described below. You must not look directly at the Sun.

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Protecting your eyes

Never look at the Sun with unprotected eyes. Intense exposure to electromagnetic radiation can destroy your retina — the cells that line the back of your eye — and cause permanent eye damage, so it's important to protect your eyesight while viewing any astronomical phenomenon involving the Sun.

Direct viewing

Specially manufactured solar viewing glasses reduce all forms of light that are known to cause damage to the eyes. Note, that while these glasses typically meet European and US safety standards, there are no Australian/New Zealand standards for solar filters. Also be aware that they are made of a thin polymer plastic that can be scratched or damaged. Do not use the filter if you suspect it is damaged.

Do not use sunglasses, smoked glass, exposed film or CD/DVDs as filters. While these objects may reduce the amount of visible sunlight your eye receives, they don't significantly reduce the amount of UV light or x-rays.

An alternative is number 14 (or greater) welding glasses. Do not use the glasses if they have been damaged, or you are unsure of their rating.

If you own a telescope, there are a range of solar filters available such as Baader film and Hydrogen-alpha. The latter type allows you to see the structure of Sun, such as prominences and flares, in fine detail. You should only use filters that attach to the front of the telescope, which filter light before it enters the tube. Never use filters that attach to the eyepiece. Naturally you cannot use your telescopes viewfinder. Make sure the viewfinder has the cap securely attached (or even remove it entirely just to be safe) so that you cannot look through it or so the Sun cannot accidently burn you through it (I tape the cap on just to make sure).

Indirect viewing

There are a number of ways you can indirectly view the Sun. All involve some form of projecting the Sun's image onto a viewing surface.

Pinhole camera

The simplest method is to make a pinhole camera. Using a sharp pin, piece a small hole in a piece of stiff cardboard. Stand with your back to the Sun and hold the card up, allowing light to pass through the hole and project onto a flat surface that is in the shade. Never look through the pinhole at the Sun. The greater the distance between the pinhole and screen the greater, but fainter, the image will be.

This method is extremely good at showing large sunspots or the partial stages of a solar eclipse.

If you are close to or on the eclipse path, look at the shadows of the leaves of trees near maximum eclipse. You will see lots of little crescents as as the gaps between the leaves act like little pinhole cameras.









Binocular and telescope projection

To see a larger, brighter image, you can use a pair of binoculars or a viewfinder to project the image of the Sun. You can project the image of the Sun onto a wall or onto a piece of white cardboard attached to a chair or some other moveable object so the projection surface can be moved as the sun moves across the sky. I use a length of dowel to attach my cardboard view screen to the binoculars.

To make viewing easier, you can put a cardboard disk or square around the binoculars so the the projected image is in the shadow. See how to set up a binocular projection system.

Never look at the Sun through the binoculars. Also, make sure that onlookers and young children do not try to look through the binoculars while you are showing them the projected image.

You can use a tripod and attachment to fix the binoculars in place, but be aware that the heat from the Sun passing through it may cause damage to the glue and lenses so give them a break every so often.

You can also use a telescope to project an image. This will give you quite a detailed image and is good for watching sunspots being covered by the encroaching Moon. Here it is best to attach the projection screen to the telescope as the image will drift significantly. Again, you have to be careful that the heat will not damage the telescope (reflecting telescopes are at risk of the secondary mirror being damaged), and that other people will not accidently look into the projecting eyepiece.

If you have a large group of people and a refracting telescope, a good projection system is the Sun funnel. Here the image is projected onto the back of a special screen. This allows lots of people to see the image with no danger of accidently viewing the unfiltered Sun. Here is an example showing how to do this using a telescope, but the same principle applies to binoculars.

About the author: Dr Ian Musgrave is an avid amateur astronomer. He writes the weekly sky updates for ABC Science and is science adviser to iTelescope.net. When not staring at the sky he is an equally enthusiastic molecular pharmacologist at the University of Adelaide, Australia. You can follow him on Astroblog for daily posts about astronomy, biology and life, the Universe and everything.





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