The article provides a brief historical and technological review of different types of telescopes, and how they were developed and improved. The telescope was invented around 1608, by the Flemish spectacle maker Hans Lipperhey. The article reports that most modern telescopes used by amateur astronomers rely on modifications to the Cassegrain optical configuration. Most of the modifications are lenses that serve to correct the spherical aberration inherent in Cassegrain's original design. In 1930, Estonian astronomer Bernard Schmidt devised a glass corrector plate that reduced the spherical aberration of a Cassegrain telescope.