Pure Russian optical excellence, no compromise optical design and construction.
"In this age of blanket computerization and convergent technology, the astronomer has to make some key choices. While weaving through the minefield that is the amateur telescope market in the 21st Century it is easy to forget that pure optical excellence is what gives the best views. If there is no compromise involved in the design and construction of an optical tube assembly it will perform to the limit of its aperture, and sometimes even seek to exceed this. This is the case with the Ylena 150, a 6" f/14 Gregory Maksutov design of unparalleled surface accuracy and smoothness. Whether used as a (highly portable) astronomical telescope or the ultimate terrestrial spotting scope this tube assembly will in my own experience equal or exceed any similar aperture on the market regardless of type, and blow far larger Schmidt Cassegrains out of the water.
I always knew the Russians made the best optics for telescopes, and had confirmed for myself that the various Maksutov designs coming out of that country far outperformed anything else on the market, even giving high end fluorite apochromatic refractors a run for the money, and at a much lower price and in a compact tube. My first session with a Ylena 150 caused me to stop and think and re-evaluate everything I had ever learned about telescopes in 33 years of observing. I have since sold my 6" refractor and 12" reflector to buy one of these. After a long search I have found what is for me the perfect observing partner."
Dr. Simon Bennet, The Widescreen Centre