... , with a fine focus of a large objective lens (adjustable 20mm), optional 250mm apochromatic objective. 3, ... damping control system that moves the optical lens can be maintained at any location within ... , eyepiece 12.5 X / 18B5, large objective lens focal length: 250mm (optional 200,300,350,400)6, cold ... with orange and green filter10, the maximum extension length of the rack arm ≥ 1000mm11, rack vertical ...