Maksutov lenses are catadioptric systems of lens and mirrors that
allow a large (and fast) diameter to be designed at a lower cost respect
to lenses. Also compactness is better. This solution unfortunately has
drawbacks, such as the quality of defocused objects, that shows a ring
of light. This is not important in astronomy however, being all stars at
infinity. No stopping is allowed, so here below you can find only the
I've tested this lens with my Canon 5D (full frame) using a 42x1 to EOS ring adapter.
Focusing is very critical and in my sample I've found the best sharpness
to be 7 mm at left of infinity mark. Focusing is hard and a Live-View
camera is highly recommended. Also focus stability is critical and I
recommend to frequently check the focus.
Optical quality is quite good all over the field, and even vignetting is very good.
Moreover this lens can be used as a spotting scope or small telescope
thanks to it's 79 mm diameter and the provided eyepiece. I've tested
under a very dark sky, and I've found the images to be quite dark
respect to equivalent telescopes, so I advise to use it in the daytime.