The Nagler eyepiece was revolutionary as the first eyepiece to deliver breath taking wide fields of view while still providing sharp images from edge to edge. In contrast to the objective of your telescope which rarely covers an image angle of more than 2°, Nagler eyepieces remain sharp over an angle of 82° to truly inspire a spacewalk vista. For this reason extreme care must be taken to correct for aberrations - especially away from the optical axis.
Al Nagler has refined this series of eyepieces taking advantage of different exotic glasses and improved coatings to deliver quite simply the best performance you can get out of an eyepiece. While other manufacturers may boast impressive field sizes, Tele Vue's philosophy of inspiring spacewalk vistas always keeps their optical devices well ahead of the pack.