Fig. 13
From: Do Leonardo da Vinci’s drawings, room acoustics and radio astronomy have anything in common?
Ray tracing of the secondary and tertiary reflectors of the Arecibo Gregorian Optics [23]. In addition to the energy of the focus, the Gregorian subreflector system also uses the energy concentrated on the part of caustic marked in red. The pair of ellipses defining the shape of the tertiary reflector is shown