Reflector or Refractor ?

In the past there has been considerable discussion on the relative merits of reflector and refractor. From the standpoint of professional astronomers, there is no serious competition between them, as each type supplements the other in a well-rounded observing program.

An amateur who plans to build his own instrument and to use it for general observing has other factors to take into consideration. Let us first look at some of the optical characteristics of reflectors and refractors.

Very early in the 19th century, when advocates of the speculum mirror began to feel the challenge of the refractor, Dr. Nevil Maskelyne, English Astronomer Royal, ventured the opinion "that the aperture of a common reflecting telescope, in order to show objects as bright as the achromat, must be to that of an achromatic telescope as 8 to 5." The relative inefficiency of the reflector of that day was due to the fact that, even under most favorable circumstances, barely 40 per cent of the original light escaped absorption by the metal mirrors, the greatest losses occurring in the short and medium wave lengths. Even silver-on-glass mirrors are subject to considerable deterioration, especially under certain conditions of the atmosphere.

Reflector or Refractor continued