The PH spot on the Optivar is used to align Phase Rings for Phase Contrast microscopy. We will deal with this later. The best resolution occurs when all elements of the microscope are in perfect alignment and the iris diaphragms are properly adjusted. August Kohler was a German microscopist who discovered the benefits of proper illumination for light microscopy, and this procedure retains his name. This is critical for photomicrography.
Procedure Examine the Stage of the photomicroscope.
Locate the knobs which move the stage in X or Y directions. These are on one side of the stage. Grasping the indicated area in the figure below can rotate this stage. This allows you to compose the best orientation for your pictures without handling the slide manually. You may not need to change the focus.