( This ( ( was ( ( ( ( ( a ( simple ( plano-convex ( or ( bi-convex lens ) ) ) ) ) , ) or ) sometimes ) ( ( a combination ) ( of lenses ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBD was) (NP (NP (DT a) (JJ simple) (NN plano-convex) (CC or) (JJ bi-convex) (NN lens)) (, ,) (CC or) (ADVP (RB sometimes)) (NP (NP (DT a) (NN combination)) (PP (IN of) (NP (NNS lenses)))))) (. .)))
This was a simple plano-convex or bi-convex lens, or sometimes a combination of lenses.
(ROOT (S (NP (DT The) (ADJP (RBS most) (JJ common)) (JJ two-lens) (NN telescope)) (, ,) (PP (IN like) (NP (DT the) (JJ simple) (NN microscope))) (, ,) (VP (VBZ uses) (NP (NN convex) (NNS lenses))) (. .)))