There are a wide range of telescopes used because the visible section of the electromagnetic spectrum is not the only spectrum that can tell us something about the universe. In fact, the visible section is a very, very, very small part of the spectrum, and any telescope that can show a different range will give us new information that wasn’t available before. With that in mind, the ultraviolet telescopes are used to read and measure ultraviolet radiation from the stars and the sun. One of the most famous and largest ultraviolet telescope is the Extreme Ultraviolet Imaging Telescope, which is housed on the SOHO spacecraft instead of on Earth. The reason that ultraviolet models don’t work well on Earth is the same reason that life is possible on earth—the atmosphere greatly reduces the number of ultraviolet rays, and thus, we all don’t get skin cancer, but we also can’t use ultraviolet scopes with any degree of accuracy.
The Extreme Ultraviolet Imaging Telescope is being used to study the corona of the Sun, because the corona is very hot, and because of the brightness of the photosphere, completely unable to be seen by the naked eye. But a telescope that takes images of the ultraviolet radiation can provide scientists with views of the sun they’ve never had before, thus giving them a greater understanding of the structure and make up of the sun’s corona. It has not been an easy thing to fund and launch this project, because there was some skepticism about whether or not this project would be scientifically useful.
Telescopes come in a variety of forms. Different companies design them for different usages.
Used telescopes can be especially useful if they are your first telescope. This can allow you to decide what type of telescope is for you before investing in a newer telescope.