... of 180 ° flip 2, with a fine focus of a large objective lens (adjustable 20mm), optional 250mm apochromatic objective. 3, the primary ... mirror with a damping control system that moves the optical lens can be maintained at any location within the 4, optical ... , Φ16.5mm, Φ10.4mm4, eyepiece 12.5 X / 18B5, large objective lens focal length: 250mm (optional 200,300,350,400)6, cold ...