The VMC200L is a unique catadioptric optical system. It incorporates a primary mirror and a meniscus corrector just before a secondary mirror. By doing so, light is corrected twice on the optical path.
The end result is that spherical aberration and field curvature are corrected to a high degree of optical performance. The VMC200L’s primary mirror is f/2.5; the compound optical system is f/9.75. This makes the system much more compact and portable than its competition.
With the optical correction placed before the secondary mirror, the VMC200L avoids the necessity of having a corrector plate and all the dewing problems associated with a closed optical tube.
An additional key feature is the rack and pinion focusing that is placed behind the primary mirror. The use of this focusing system eliminates the image shift associated with most other SCT systems. This is especially important when using high power magnification or astro-photography. When focusing, the image is stable and easy to adjust.