TS Ploessl 15mm
Very good sharpness, just close to the edge a little bit worse.
x-axis: distance from optical axis in °, y-axis: resolution in arc minutes
Apparent Field of View:
The apparent field of view is approx. 39°
Very good contrast because of good multicoating and use of just four lenses.
Simple, but not bad. Unfortunately no blackened filter thread.
Very good and inexpensive Ploessl.