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Aperture
Aperture is the diameter of the main telescope mirror or lens and the most important feature of a telescope, because it determines the amount of light that is collected. Greater apertures produce brighter, and generally clearer, images than smaller apertures. Reflectors offer greater aperture per dollar than refractors because reflector optics are easier to manufacture. At apertures greater than three inches, refractors become increasingly expensive, as compared to reflectors of the same size. A six-inch refractor, for example, typically costs two-to-three times as much as a six-inch reflector equipped with the same accessories.
Chromatic Aberration
A major disadvantage of refractors is they produce color-fringed images. This false color results from inability of the objective lens to bring all the colors (wavelengths) of light to focus at a single surface, or plane. Reflectors are free of this effect because light is reflected to a focus rather than refracted; it does not pass through a glass medium. High-end refractors reduce chromatic aberration to near imperceptibility, but apertures larger than four inches are unaffordable for most people.
Use and Portability
Another disadvantage of refractors is weight. Large refractors, those with apertures greater than four inches, are very heavy and can be difficult to use and transport. A six-inch reflector on a German equatorial mount is much easier to work with and transport than a six-inch refractor using same mount design. Refractors have longer and heavier optical tubes and therefore require heavier mounts.
Refractors with apertures greater than five inches require two people for transport and setup, whereas a six-inch reflector is easily handled by just one adult.
Refractor vs Reflector
Commercially available refractors come in a range of sizes and sophistication level. All of them use the same optical principle, whereby light is refracted (bent) to a focus at the rear of the optical tube. An eyepiece positioned there magnifies the focused image. The more expensive refractors, such as those of apochromatic lens design, are highly corrected, precision-manufactured instruments that produce sharp, color-free images. Images produced by refractors are generally superior in quality to those produced by reflectors of the same aperture. High-end reflecting telescopes, such as those of Maksutov-Cassegrain optical design, can produce images that rival in quality those of the best refractors.