6mm orthoscopic (Japan), about 25 years old
Very good sharpness, becomes worse just close to the edges.
x-axis: distance from optical axis in °, y-axis: resolution in arc minutes
Apparent Field of View:
Field of view is 39°.
Not good, but not terrible. In comparison one will see, that today’s multi-coatings are clearly an improvement.
Not too bad despite the short focal length.
Simple, but not bad.
Not really a good eyepiece, but not a deterrent example.