An ultra-wide-field eyepiece designed in 1980 by the American optician Albert Hirsch Nagler (1935– ). Characteristically it is a complex seven-element design (the Nagler-2 has eight elements) that produces an 82° apparent field of view while correcting for spherical and chromatic aberration, coma, astigmatism, and field curvature. Its eye relief is very generous, and the performance at the edge of field is excellent. The design is optimized to work with focal ratios as fast as f/4.
Subjects: Astronomy and Astrophysics.