29 May 2012

How to observe the transit of Venus

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Want to observe the transit of Venus but don't know how? You can observe the historic moment even if all you have is a kitchen colander, a smartphone, $5 or a piece of paper.
How to observe Transit of Venus

There are lots of ways to observe the Transit of Venus. Credit: NASA

Only two planets – Venus and Mercury – have transits that cross the Sun and are visible from Earth. Mercury’s transits are far more regular, occurring 13 times a century. The transit of Venus, however, occurs only twice (in a pair eight years apart) every hundred years or so. With the next transit occurring on June 5th/6th this year (the backend of the 2004 – 2012 pair) this is your last chance to observe the Transit of Venus until the next pair begins in 2117.

So if you’re going to make the most of the June transit the the best place to be is eastern Australia. It will be one of the few regions to witness the entire transit, which lasts six and a half hours. If you live in on the East Coast of Australia, you will see the transit from 8.16am to 2.44pm. Meanwhile, those in Western Australia, India and Europe will see a partial transit at sunrise on June 6 and North America is set for a partial transit at sunset on June 5.

Protect your eyes! Try solar glasses

When watching the transit make sure you don’t look directly at the Sun! You’ve heard it’s dangerous and it is – it can cause serious and permanent damage. The retina doesn’t have pain receptors so you won’t feel any pain to warn you even if you are causing injury. Luckily, there are a few great ways to see the transit safely. (No, using sunglasses are not one of them.)

If you do want to look to the sky, you can use a telescope with a solar filter or, the recommended protection is welder’s glasses, number 14. If you don’t have these lying around the house, there are also
solar glasses
, which can cost as little as $5 from the Sydney Observatory. There are some
safety standards
around such glasses, however, Australia doesn’t have its own standards regarding safety.

Simple pinhole solar viewer

The simplest method is to create a pinhole solar viewer using just a pin and some paper. Just poke a hole in one piece of paper and hold it up with your back to the Sun. Then hold another piece of paper underneath the first one and move it back and forth until you get a focussed image of the Sun.

But, if you want to watch it for all six to seven hours, you don’t want to standing with your hands in the air. In that case, try the pinhole trick in a box, where you cut an opening in the top to watch the Sun’s projection.

You can also try using a kitchen colander for a lovely collage of many little Suns.

Best viewing: large projections from telescopes

Finally, if you want a group of people to watch the transit at once, large projections from telescopes or binoculars are the best way to go. Just like the pinhole viewer, set up the telescope or binoculars (with one eyepiece blocked) towards the Sun with the eye piece facing a wall or cardboard and then focus the image.

However, you will just need to be careful that nobody looks into the projection line and that the binoculars don’t overheat.

Bad weather? Bad position? Try livestreaming

Despite all the methods, none will work if you can’t see the Sun – whether it’s because you’re in an area of poor visibility, it’s cloudy or you just have too much to do. If that’s you, the transits will be streamed live from the Sydney and Perth observatories by the RI Aus, and by NASA from the Mauna Kea Observatory in Hawaii.

While you’re watching the transit you can also experience what it was like for James Cook to measure the length of Venus’ transit with an app developed by Astonomers Without Borders on your smartphone. You touch your screen when Venus starts and finishes transiting across the Sun. (This is more difficult than it sounds, because Venus makes a teardrop shape as it touches the edge of the Sun. Don’t worry – the app includes a feature that allows you to practice before the big day).

From the app, your times and location will be uploaded to an online depository with data from around the world, and you can edit your contribution with images, videos or stories from the day.

COSMOS and NASA challenges

If you manage to get some good snaps of the event, be sure to send them to the COSMOS team to enter the COSMOS Transit of Venus Competition. The best seven photographers will win a copy of Nick Lomb’s Transit of Venus: 1631 to the Present and a one-year digital subscription to COSMOS.

If you love maths, you can even use your photos to calculate the Astronomical Unit, the mean distance between the Earth and the Sun, for which the official value is 149 million kilometres. In 1769, Captain Cook measured it to be 153 million kilometres, so you can compare the accuracy of your modern-day methods.

NASA’s Venus Transit Observing Challenge, where you can use measurements from your own photo (or other people’s photos) for the calculation. And at the end of it you can print off a lovely certificate from NASA for completing their challenge!

We may no longer require the Transit of Venus to helps us measure the size of our Solar System but the transit isn’t obsolete, it’s now helping us understand space outside of our Solar System. This year, some scientists will use Venus’ transit to test the accuracy of calculations which can identify when a star’s brightness dims due to a planet passing in front of it – which is crucial for the identification of exoplanets outside our Solar System.

Perhaps we will have a completely different scientific purpose for the next Transit of Venus. But until then, you can send in suggestions for what people should read at the next transit, in 2117, with the Transit of Venus time keg at TransitofVenus.org.

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