Your First Telescope . Articles | ... Modern amateur telescopes can be divided into three classes: . 1) The refractor is what most people think of when they hear the word "telescope". ... Refractor disadvantages: Some secondary color ("chromatic aberration") still visible in all but the best units, large aperture instruments can be massive, most expensive of the three designs (often by a large margin), "Guilt By Association" with horrible department store refractors. ... www.astronomy.net . ...