There have been zoom eyepieces in the past, but none quite like the Tele Vue 3mm-6mm Nagler Zoom. Since the time of Galileo, short-focal-length (hence high-magnification) eyepieces have been notoriously difficult to look through. That has changed in recent years, especially with the introduction of Tele Vue’s wide field Nagler designs. The new Tele Vue Nagler zoom eyepiece is small and lightweight, but maintains a constant focus and 50 degree apparent field. It also lets observers choose in-between focal lengths, thus giving them the ability to tune the magnification to atmospheric conditions, which is very critical for high-power viewing.
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.