Here are all the eyepiece files for p 18, p 19, p 20, and a few others (see http://www.users.bigpond.com/pjifl). This replaces the previous file I sent you as it contains that plus more. There is now a much wider range of eyepiece types represented here now which may be useful to people interested in teaching themselves eyepiece design. There is now an Abbe type, and a simplified 'Nagler' type, a simple triplet, and some 12 Konig types. The larger eyepieces from pp 18 - 20 also have reverse traced files. Download here.