When do you use the course adjustment knob on the compound light microscope?

The course adjustment knob on a compound light microscope is used for making large changes in focus when initially locating a specimen. It is typically used with low-power objectives to quickly bring the specimen into view. Once the specimen is roughly focused, the fine adjustment knob should be used for precise focusing. Using the course knob with high-power objectives can risk damaging the slide or the lens.