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how does LASCO see the corona?


Why doesn’t a burning candle look as bright in daylight as it does in a dark room? Well, the daylight is much brighter than the candle and it swamps the light from the candle making it harder to see.


The same thing happens when we try to look at the Sun’s atmosphere, the corona. Light from the corona is completely swamped by light from the Sun’s disk. We need to block out the light from the disk.




The corona is made of very hot plasma and does give off some radiation of its own, mostly ultraviolet and X-rays. It also scatters some of the visible light which comes from the Sun's disk. It's like the way a torch beam can be seen when the atmosphere is dusty or foggy. This scattered light is very, very faint and we have to block out the Sun's disk to stand a chance of seeing it. This is what a coronograph is for.

A coronograph is just a telescope with a disk that blocks out the bright light from the Sun’s disk and lets you see the surrounding corona - just like the milky water experiment.


Bernard Lyot built the first coronograph. Here he is working at the Pic du Midi Observatory in France.



Courtesy of the High Altitude Observatory, Boulder, USA

You can see more movies in our Gallery [Movie file 1mb or more - High quality]



Here are some images of a CME eruption taken with a coronograph at the High Altitude Observatory


Lyot's coronograph was a great invention. Even so, observations of the corona from Earth are still very difficult because of the very bright daytime sky. We get a much better look at the corona from space because there is no bright background glare from the sky.




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