 Solar AstronomyFor many years astronomers have enjoyed observing the Sun through 'white light' filters that just reduce its intensity to safe levels. This shows interesting views of sunspots and several other surface features. But in recent years a new type of filter has emerged onto the amateur market that makes it possible to see much more, including flares and prominences coming out of the Sun's surface. Flares and prominences are often associated with material being flung into space, some of which heads in our direction causing 'space weather' that can damage satellites, increase the aurora, and interfere with ground communications and electricity supplies. To be able to observe solar flares requires a very narrow band filter carefully tuned to the hydrogen alpha light emitted by the flares. This cuts out most of the Sun's background light whilst letting through the hydrogen alpha light. The device used to do this is called a Fabry-Perot etalon. The first telescopes to bring this technology to the amateur cost several thousand pounds. These are still available and are used where the highest quality images are required. However, Coronado realised that very good images could be produced by passing the light through a much smaller and less expensive etalon. They built this idea into their Personal Solar Telescope (PST) thus bringing a whole new experience to the amateur astronomer. The basic PST is a delight to use and is great for watching how the Sun's activity changes from day to day, or even hour to hour. When you see a flare changing shape, and realise that it is many times the size of the Earth, you start to appreciate the enormous amounts of energy involved. | 
