This is a 'real' demonstration of the transit method used to detect extrasolar planets, but using our somewhat closer neighbour Venus.
As Venus passes in front of the sun in this video, there is a small (less than 0.1%) reduction in the overall light reaching the camera. The time-varying light level is shown on the graph. We see the exact same thing happening to many of the stars in our galaxy when we look at them with sensitive instruments such as the Kepler observatory.
The footage is a time-lapse movie of the transit of Venus which I observed from Australia in 2012. It was photographed with quite modest equipment, so it was a challenge extracting any sort of light curve due to noise, camera vignetting and atmospheric effects. After some quite heavy processing I managed it, and although far from perfect I think it serves the purpose.
I've made the video available for download under a CC license for public talks, teaching etc. You should be able to download a copy of the video here on Vimeo (somewhere above).
There are some animated GIF versions here: wp.me/p2oitj-70
Some more information on the transit method on Wikipedia: en.wikipedia.org/wiki/Methods_of_detecting_exoplanets
Here's the original time-lapse of the transit (longer than this video and with cool music): vimeo.com/61451703
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