4mm orthoscopic by Meade, about 25 years old
Sharpness:
Terrible. Bad at the center, it becomes worse 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°.
Contrast:
Very bad, the multi-coating does not help.
Aberration:
Cushion distortion, field curvature and chromatic errors are visible.
Eye Relief:
Uncomfortable as expected at this short focal length.
Mechanical Quality:
Light-weight eyepiece because of aluminum sleeve. Simple, but not bad.
Summary:
Something for the trash can. However, Meade sold it as a medium-priced
eyepiece. Manufacturing of this eyepiece has been stopped years ago – good
decision.