“This is a triplet airspaced Fluorite APO, where the Fluorite is used as the center element. It is my
personal telescope, which I got as a handselected sample in the early 90'ths, after my first
sample did not pass my expections. The startest shows a better quality than the Zygo testreport. Probably because the lens does not have the best uniformity and shows in this report some smaller zones, which are not detectable in the above startest. The colorcorrection of this lens is far better as we see on the above images, maybe the CCD camera or the ortho eyepiece used for eyepieceprojection gets in some trouble with such a fast system. The lens is smooth and shows an overal good spherical correction. On some starparties in a side by side comparision when observing Planets and Double-Stars many users have confirmed, that this lens shows the same razorsharp images as a handpicked Zeiss APQ 150 and might even beat some other famous 6" ED Apos. To see such small differences again very high powers are necessary. At the time when I bought this scope there was nothing better on the market, today the choice is larger and one could obtain the same quality for less money”
Markus Ludes (APM-Telescopes)
This 6" refractor shows an artificial obstruction image due to the secondary of the Maksutov Newtonian collimator. The obstruction is about 37% in diameter.