miroir primaire

CONT: On peut citer quelques formules optiques : le télescope de type Newton, qui utilise un miroir primaire concave sphérique ou parabolique et un miroir secondaire plan, c'est le montage le plus simple et le plus ancien, utilisé actuellement dans beaucoup de constructions d'amateurs. Il a été mis au point par Isaac Newton, le miroir plan est incliné à 45° et permet de renvoyer l'image focale à 90° de l'axe optique près de l'ouverture du tube.

CONT: The primary mirror is located at the lower end of the telescope tube in a reflector and has its front surface coated with an extremely thin film of metal, such as aluminum. The back of the mirror is usually made of glass, although other materials have been used from time to time. Pyrex (trademark) was the principal glass of choice for many of the older large telescopes, but new technology has led to the development and widespread use of a number of glasses with very low coefficients of expansion.