FOCUSING WITH OIL IMMERSION - Olympus CH-2 Microscope (see Fig. 1)
1. Before you plug in the microscope, turn the voltage control dial on the right-hand side of the base of the microscope to 1. Now plug in the microscope and turn it on (see Fig. 1B).
An alternate focusing technique is to first focus on the slide with the yellow-striped 10X objective by using only the coarse focus control and then without moving the stage, add immersion oil, rotate the white-striped 100X oil immersion objective into place, and adjust the fine focus and the light as needed. This procedure is discussed in the Introduction to the lab manual.
2. Place the slide in the slide holder (see Fig. 1A), center the slide using the two mechanical stage control knobs under the stage on the right-hand side of the microscope, and place a rounded drop of immersion oil on the area to be observed.
3. Rotate the white-striped 100X oil immersion objective until it is locked into place. This will give a total magnification of 1000X.
4. Turn the voltage control dial on the right-hand side of the base of the microscope to 9 or 10 (see Fig. 1B). Make sure the iris diaphragm lever in front under the stage is almost wide open, (toward the left side of the stage; see Fig. 1B), and the knob under the stage on the left-hand side of the stage controlling the height of the condenser is turned so the condenser is all the way up.
5. Watching the slide and objective lens carefully from the front of the microscope, lower the oil immersion objective into the oil by raising the stage until the lens just touches the slide (see Fig. 1A). Do this by turning the coarse focus (larger knob; see Fig. 1B) away from you until the spring-loaded objective lens just begins to spring upward.
6. While looking through the eyepieces, turn the fine focus (smaller knob; see Fig. 1B) towards you at a slow steady speed until the specimen comes into focus. (If the specimen does not come into focus within a few complete turns of the fine focus control and the lens is starting to come out of the oil, you missed the specimen when it went through focus. Simply reverse direction and start turning the fine focus away from you.)
7. Using the iris diaphragm lever, adjust the light to obtain optimum contrast (see Fig. 1B).
8. When finished, wipe the oil off of the oil immersion objective with lens paper, turn the voltage control dial back to 1, turn off the microscope, unplug the power cord, and wrap the cord around the base of the microscope.