Окуляр SuperView 30 mm Wide Angle (Erfle) 2"

Ideal for low magnification observations or afocal photography. These 2" eyepieces from GSO provide wide field of view despide the long focal length. The 5 elements privde well corrected field of view. All air-glass surfaces are fully multi coated. The longest focal length model with 50mm can be used in F/8 or slower telescopes.

The ERFLE eyepiece - this eyepiece has an extra positive element, and the form of the lenses is different. It has a concave surface near to the intermediate image. This surface reduces Petzval sum, and it also helps to achieve a longer eye relief by moving the chief rays away from the axis. The semi-field angle for this design is 30 deg. In this example, the lateral color is not corrected, because the eyepiece is intended for use with a prism. This is a typical eyepiece for use in afocal systems of reasonable quality.