Baader 1.25" Classic Ortho 6mm (HT-mc) eyepiece - original Zeiss Ortho design. We recommend the Classic Orthos from Baader to all observers who value the brightest possible image with optimum sharpness on the axis. The eyepieces are particularly suitable for planetary observation and photography (eyepiece projection double star observation, but also for observing deep-sky objects where a large field is not important. Classic orthoscopic eyepiece design according to Ernst Abbe's design, completely distortion-free image, 1.25" receptacle without locking groove. The Baader Classic orthoscopic eyepieces are parfocal - it is not necessary to adjust the focus. Focal length: 18mm Insertion diameter: 1.25" without locking groove