He developed the first reflecting telescope, which featured a concave mirror, a flat mirrow & an eyepiece
If the eyepiece is changed to a 15 mm lens, the magnification will be 610 mm/15 
mm = .... convex shape on the other, while plano-concave means the lens has a 
plane... [DOC] [TLE] Download Sample pages 1 PDF - Springer [PAR] Instead of using a convex lens to ... tube to a tiny flat mirror, mounted centrally 
and at a 45 degree angle, delivering the light cone to the eyepiece, where it 
reached focus.