Switch to the 10X objective into the optical path. Without using the coarse and fine focuses knobs, adjust the focus on your dominant eye using the diopter rings. Then, adjust the focus on your non-dominant eye by rotating the diopter
ring.
Next, switch from the objective lens 10X to 40X and focus with the fine focus knob.
Repeat steps 1-3 twice.
Your adjustment is complete if you do not notice any differences between your left and right eyes when you look into the eyepieces using the 10X and 40X objectives.
