 Solar Observation in H-alpha Light H-alpha light is given off by excited hydrogn atoms in the Sun's atmosphere and by isolating it and blocking out all other light from the Sun we can see features that are normally hidden. For example, flares and prominences that are visible during a total eclipse can be seen any day that the Sun is shining in a clear sky. Surface features such as flares travelling towards us can be seen together with white-light phenomena such as sunspots. Until recent years this kind of view of the Sun was only available to research institutes using extremely expensive equipment. But pioneers such as Coronado have made the technology available to the amateur market. At the heart of an H-alpha telescope is a Fabry-Perot etalon, a finely-tuned filter with an extremely narrow bandwidth. Used in conjuction with an energy rejection filter and an order sorter this enables us to isolate the H-alpha light safely. The best H-alpha telescopes have etalons that are the same size as the telescope aperture and you should choose one of these if you want the best performance. But etalons are expensive so Coronado have developed the Personal Solar Telescope (PST) that uses a smaller etalon to provide fascinating views at a fraction of the cost. | 
