Tele Vue's Powermate™ focal extenders, present a technically universal solution using a positive field lens to redirect field rays. The result is an exit pupil that stays where the eyepiece designer intended
Tele Vue's Powermate™ consists of a negative doublet plus a positive "pupil-correcting" doublet. This 4-element system provides the magnifying function of a Barlow without its limitations by restoring the field rays back to their original direction, as if the Powermate™ were not there. The result is a pure magnification increase.