(a) Draw neat, labelled ray diagrams for a refracting astronomical telescope and a reflecting (Newtonian type) astronomical telescope, both adjusted for final image at infinity.
(b) From the diagrams in part (a) identify any three structural or optical differences between the two instruments.
(c) Give two distinct reasons why instruments intended to have an aperture larger than 4 m are almost always built as reflecting telescopes and not as refracting telescopes.
(d) Explain qualitatively why a reflecting telescope is free from chromatic aberration whereas a refracting telescope suffers from it.