Soligor Ploessl 4mm
Sharp to the diffraction limit of the measurement device in the center, but not good towards the edges.
x-axis: distance from optical axis in °, y-axis: resolution in arc minutes
Apparent Field of View:
The apparent field of view is approx. 48°
For this focal length astonishing good.
Very short eye relief because of the short focal length. Folding back the rubber eye cup make it easier.
Like the Skywatcher and TS Super Ploessls.
Fine for a 4mm eyepiece.