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Since looking directly at the Sun with the naked eye permanently damages vision, amateur observation of sunspots is generally conducted indirectly using projected images, or directly through appropriate protective filters designed for the purpose. Small sections of very dark [[optical filter|filter glass]], such as a #14 welder's glass are sometimes employed in the latter capacity. The eyepiece of a telescope can also be used to project the image, without filtration, onto a white screen where it can be viewed indirectly, and even traced, so sunspot evolution can be followed. Special purpose [[H-alpha#Filter|hydrogen-alpha]] narrow bandpass filters as well as [[vacuum deposition|aluminum coated]] glass attenuation filters (which have the appearance of mirrors due to their extremely high [[optical density]]) are also used on the front of a telescope to provide safe direct observation through the eyepiece.
Amateur observers are strongly advised not to make use of filters, no matter how dark, which are not specifically intended for solar viewing. Such filters may not provide appropriate protection in the non-visible frequency range and eye damage could result. If a telescope or pair of binoculars is being used for direct viewing with a filter, the manufacturers' guidelines should be followed closely. These will usually require the filter to be placed at the objective end of the equipment rather than the eyepiece, since heat concentrated by the equipment may melt or fracture any eyepiece filter and cause immediate eye damage. Care should be taken to ensure that the filter is securely fastened, and that attached auxiliary devices such as spotter scopes are hooded in case they concentrate heat dangerously. In general, direct observation of the sun's surface through an optical device is an inherently dangerous practice, and requires both knowledge and close attention to safety precautions if it is to be undertaken.
==Application==
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