This tip should be followed because using the coarse focus knob on the high power objective lens can result in damage to the specimen or the microscope. The high power objective lens has a shorter working distance, meaning it is closer to the specimen compared to the lower power objective lenses. The coarse focus knob adjusts the distance between the specimen and the objective lens. If the coarse focus knob is used on the high power objective lens, there is a higher risk of the objective lens colliding with the specimen or touching it too closely, potentially causing damage. Therefore, it is recommended to only use the fine focus knob on the high power objective lens to make small and precise adjustments without risking any harm to the specimen or the microscope.
