I emailed Kasai a link to this thread and asked for comment. Here's their reply:
The PICO-8 with severe spherical aberration was among the batch supplied to a dealer in Denmark last year.
I could know this fact because it was said as the interior paint was badly peeled off - It was among the ones sold as “factory second” for half price. (And I believe the end user should have paid half price for it, too.) Concerning those units, it’s true that there were some with poor optical performance.
However, such a defective unit is never supplied as long as it’s sold for regular price.
Also I dare to emphasize the fact that we do perform visual test on each unit with artificial stars - to check the residual aberration, collimation and mirror shift.
Somebody who bought PICO-6 suspected us of this fact, as the brass ring in the eyepiece adapter was bent and it couldn’t accept an eyepiece easily.
I feel sorry we forgot to check this defect on this case, but still this has nothing to do with our visual test.
As mentioned above, we use artificial stars for the visual test, and, to reach the focus, some stacked M42 extension tubes are used. (As you see in our catalog, PICO has M42 threads outside the eyepiece adapter.) As a result, when testing, the original 1.25” eyepiece sleeve is not used.
And, concerning the collimation, of course we adjust each unit to the best collimated condition before shipment.
However, as there are only 3 “push & pull” collimation screws and no “stopper screws” are provided, sometimes (especially when exported) it becomes misaligned because of the rough treatments during the long transport. Still, the user can re-collimate it rather easily - just see a bright star (or artificial stars) in the center of the field and adjust the collimation screws for the defocused star image to be concentric and the focused image to be round with a few uniform diffraction rings
By the way, unfortunately the delivery of PICO-8 is delayed.
They were delivered from the factory late last month, but we found a mechanical problem in every unit - now we are discussing with the factory to solve it.
I never want to supply defective units to our customers. I think this problem can be solved and make shipment within 1-2 months. Thanks for your patience.
A superfluous information:
The same scope is supplied by Omegon, Germany. The basic features are the same as PICO-8, but there is one important difference. Omegon’s has a very thick secondary baffle, and it causes a pretty vignetting on the clear aperture. Concretely speaking, it is not 80mm f/11 but practically 60mm f/15. Of course the star image may become sharper (with smaller aperture and slower f-ratio), but the light gathering power and the resolution are much inferior. To avoid this serious problem, we have asked the factory to remove this evil secondary baffle from every PICO-8, to keep 80mm full clear aperture.
Edited by MortonH, 10 September 2016 - 08:27 PM.