The dissecting microscopes usually use reflected light, bouncing off the surface of the specimen before reaching your eyes. It also allows you to perceive depth, because the two eyes see the specimen through separate lenses. The magnification of the dissecting microscope is not as great as the compound microscope. It does, however, enable the viewer to observe large specimens at a magnification up to 30X.
The head of the microscope, known as the power pod, has variable power magnification ranging from .7X to 3X. To calculate the magnification of your specimen, multiply the setting of the magnification knob by 10, the power of your eyepieces. Proper adjustments of interocular scale and diopter adjustment ring will achieve the same state of focus in the left and right eyepieces on the dissecting microscope just as they did for the compound scope.
The diopter ring can be located just below the ocular lenses and the interocular scale can be located on top of the head just under the ocular lenses. Look into the microscope with both eyes and hold the eyepiece tube with your left and right hands. If you see one field, no adjustment is necessary. If you see two fields, move the eyepieces in either direction (push together or pull apart) until one field is visible. Note the number of the interocular scale for future use.
The eyepieces have a range of eye spacing from 50 mm to 70 mm. If one eyepiece is moved, the other which is linked to it, will also move. Record the Interocular Scale Number; this is your personal setting for use on the microscope you have been assigned. The eyepieces can be focused separately. Set the magnification knob at 3X and using your right eye only, rotate the right diopter ring to the same reading on the interocular scale. Adjust the focusing knob until your specimen is in focus. Reset the magnification knob to .7X and using your left eye only, rotate the eyepiece adjusting ring either way until your image is sharp. If your vision differs a great deal from one eye to the other, start your adjustments with the stronger eye. As with the compound microscopes, each time you use the dissecting microscopes, you should check for loose or damaged components, clean the lenses, and notify the instructor if problems are noted.
Each dissecting microscope is provided with a Nicholas illuminator. The three-step variable transformer provides a concentrated beam of high intensity light. This illuminator can be mounted three ways for an optimum directional spotlight. The illuminator can be inserted into the hole in the back of the base of the microscope and the substage mirror rotated to allow for transmitted illumination (through the specimen, as in the compound microscope). The illuminator is usually inserted into the circular opening on top of the arm, to provide reflected light. A versatile light positioning may be obtained by inserting the illuminator into the mounting ring of the adapter arm extending from the transformer.
