Microscope use

Set up:

1. Remove the microscope from the cabinet. Carry it with both hands: have 1 hand gripping the arm, the other hand under the base.

2. Before plugging the scope into the electrical source, check to make sure that the light is off. The on/off control is on the base of the scope on the left-hand side.

3. Plug the scope into the electrical socket.

4. Turn the light on using the on/off control on the base of the scope. Whenever you adjust the amount of light passing through the specimen, use this control.

5. Make sure the condenser is raised up as far as it will go.

6. Open the condenser diaphragm about half way using the lever on the condenser.

7. Open the clip on the mechanical stage and insert a prepared slide, positioning it so that the stained section is over the hole in the stage below the objective lens.

Focussing: note:

1. Rotate the 10x objective lens into position. Look through the oculars, noting that there is a pointer in one of the eyepieces. Adjust the light intensity to a comfortable level using the on/off control on the base of the scope. Touch up the focus using the coarse and fine focus knobs, which are located on either side of the arm of the scope. Note: If you have trouble finding the specimen because it is lightly stained or very small, try the following: Place the edge of the coverslip over the hole in the stage below the objective lens. Using the coarse focus knob, focus on the edge of the coverslip. Now, use the stage controls to bring the specimen itself into view.

a. This is a binocular scope - use both eyepieces when using this microscope - using just one eyepiece will cause eye strain. Adjust the distance between the oculars so that it is comfortable for your eyes (everyone has a slightly different interpupillary distance). You should see 1 circular field it the distance between the oculars is adjusted correctly.

b. Adjust the focus for each eye. The scope is made so that the focus can be adjusted independently for each eye (generally the eyes have a slightly different focus, even in the same person). Use the following procedure to adjust the focus for each eyepiece:

i. With the low power objective lens (10x) in place, close the left eye and bring the specimen into focus using the fine focus knob. The right objective is now focussed.

ii. Now, focus the left ocular by closing the right eye and bringing the specimen into focus using the ring on the left eyepiece.

2. Because the scopes are "parfocal" you should now be able to switch to any of the higher power lenses without having to do much focussing. Note: You should not have to use the coarse adjustment again during the whole lab period because all the slides are all of about the same thickness- use the fine focus only to sharpen the focus. Before you switch to the 40x lens, make sure the part of the slide you are interested in seeing at a higher magnification is in the center of the field before you switch lenses.

3. Now, switch to the 40x lens (a relatively high power lens - alias the "high dry"lens) and using the fine focus - bring the specimen into focus. Notice that as you switch to the higher power lenses you may have to increase the amount of light passing through the specimen by using the on/off control on the left hand side of the base of the microscope. This is necessary because the higher power lenses are smaller than the lower power lenses and less light passes through them.

4. To use the 100x (oil immersion lens), bring the feature of interest into focus with the 40x lens. Before you switch to the 40x lens, make sure the part of the slide you are interested in seeing under oil is in the center of the field before you switch lenses. Then rotate the 40x lens out of position so that the 4x (low power lense-the shortest lens) is in position over the specimen. Now, place a drop of oil on the coverslip directly over the area of the slide through which the light passes. Rotate the oil immersion lens into position over the specimen. It will contact the oil. You may have to again increase the amount of light passing through the specimen. Do this by using the on/off control on the left-hand side of the base of the scope.

After examining the specimen, rotate the oil immersion lens away from the specimen. Be sure to rotate a low power lens (4x) NOT THE 4OX LENS over the specimen when you rotate the oil immersion lens out of position. Wipe oil from the oil immersion lens using lens paper. If you ever get oil on the 40x lens, clean it off immediately with a piece of lens paper. If you cannot get a sharp focus with any lens after trying to clean it yourself, get help from your instructor. It may be contaminated with oil.

5. Remove the slide from the stage by simply opening the clip on the mechanical stage and removing the slide. Do not lower the stage with the coarse focus - just slip out the slide. Clean any oil from the slide with a Kimwipe and if (Heaven forbid) you got oil on the stage, clean it off with a Kimwipe. You can now put another slide on to the stage and it should be in focus. Adjust the focus using the fine, not the coarse focus.

Clean up:

Put the microscope away in the cabinet with the arm facing out and the code number of the scope clearly visible. Make sure that the number of the scope corresponds to the number on the shelf.

Note: At any power, you can increase the contrast between various parts of the specimen optically by "closing down" the substage condenser diaphragm. Practice adjusting the amount of light coming through the specimen with the on/off switch and the substage condenser diaphragm control in conjunction.