Technical information

         The most used system is the  Newtonian reflector  invented by Sir Isaac Newton according to the drawing on the side. This system  eliminated  the refractors’ chromatic aberration, since the primary mirror reflects the light. The modern refractors are achromatics, but they can’t eliminate totally the cromatism. However the reflector mirror should be parabolic, since the spherical mirror has a great aberration, depending of the focal distance, that endangers the image.






















Projection of a simulated star for test of astigmatism





Geometrical explanation of the Foucault test !!!

















 16" pirex, f 4,8  for correction!





central elevation, edge down, 


foucault, test  ronki  100 lines





paraboloid !! (16" f-4,8)

foucault test , ronki  100 lines

 Texereau!! métod

^ = 0,368 = 2,73=5,76 = 8,75




Plano convex lens




Achromatic lens