Photographic version with removable 2" stop ring, usable optionally with T2 (M42x0.75) or M48x0.75 connection. Coma corrector for Newton telescopes that does not extend the focal length of the telescope and does not reduce the image field. Large lenses for completely vignette-free images up to f/3.5. Highest sharpness performance across the entire image field. Phantom Coating - group multi-coated for maximum transmission and reflection-free performance.