Stellarvue's SVX Optics have the highest optical ratings as measured and documented on our Zygo Phase-Shifting Laser Interferometer. To get optics to this level of accuracy takes between six to nine months.
The quality of an astronomical optic is generally measured in Strehl ratio, introduced by the German physicist, Dr. Karl Strehl. A theoretically perfect lens would have a Strehl ratio of 1.0 so under this system optics are rated at a fraction of the number 1. The higher the fraction, the closer to perfection an optic is.
Most mass-produced, commercial optics we have tested are generally rated at about .8 - .9 Strehl. SVX series optics that are 102 mm and larger are rated at .99 - .996 Strehl meaning that 99% of the light is going exactly where it is supposed to go. Our 80 mm triplets are rated at .98 Strehl or higher.
Strehl ratio is an excellent comparative measurement but it takes more than a high Strehl number to make a world class optic. Aberrations commonly seen in mass-produced optics must also be reduced to a fraction of what is normally allowable. This includes astigmatism, spherical aberration, coma and trefoil. It took us many years to develop the time intensive processes we use to make premier optics. Once we developed our processes in 2018, we moved from .95 Strehl to .99 Strehl as a standard and all the aberrations normally considered allowable in machine made optics were reduced by a factor of five. The result is an optic as close to perfection as we can make.
Stellarvue SVX optics are made for discriminating observers and imagers who know the best when they see it.