Think of the coarse adjustment knob as the door opener. Imagine you’re trying to find a lost earring in a shaggy carpet. You wouldn’t stare at one tiny spot and wiggle your fingers—you’d sweep your hand around until you feel the metal. That’s exactly what this knob does: it gets you in the ballpark, fast.
When you sit down to look at a slide, everything is blurry and hopeless. The sample might be an inch above or below the lens. The coarse knob is your closest friend here. A few quick turns, and suddenly you see a faint shape, a shadow of something amazing. You haven’t found the treasure yet, but you’ve opened the door to the room where it lives.
