1. Look through the eyepiece and adjust the distance between the eyepiece tubes (14) by  grasping the head, by its four gripped corners (13), and moving it horizontally.  2. When a full field of view is observed through both lenses, and images blend into one, the  interpupillary distance is correct for the user’s eyes. Take note of the index reading marked  in the interpupillary scale (2) for the following step.  3. Adjust the diopter scales (14) situated on both eyepiece tubes until the reading of both  scales coincides with the value of the interpupillary distance scale. This step is necessary to  maintain the parfocality of the objectives. 4.  Readjust the diopter scales for variation in interpupillary distance. 1. Turn the revolving nosepiece (3) and place the 4X objective (4) in the optical path ensuring  that it is properly clicked into place. 2.  Turn the coarse focus knob (19) until the stage (8) is in its lowest position. 3.  Place a microscopic sample on the stage, make sure the cover slip faces upwards. •  Swing the moveable finger (5) on the mechanism (6), place specimen against fixed side  of slide holder (7) and gently release the moveable finger until the specimen is  supported in place.  4. Make sure that the specimen is in the optical path by adjusting the stage using the knobs  controlling the X/Y movements (21).  5. Looking through the eyepiece, turn the coarse focus knob until the preparation appears in  focus. 6.  Readjust the focus with the fine focus knob (20) until the image appears sharply defined. 1. With your right eye, look into the right eyepiece tube (1) and adjust the sharpness of the  image using the fine focus knob (20).  2. With your left eye, looking through the left eyepiece, adjust the focus by rotating the diopter  corrector (14) on the left hand eyepiece tube until the image is sharp. Do not use the fine  focus knob. The aperture of the diaphragm (9) should not be used to control the brightness of the light.  Diaphragms are designed to obtain high resolution of the sample, and provide contrast in the  image. Smaller apertures will deliver higher contrast to image. However, closing the aperture  too much will reduce resolution. Experimentation is the best method of determining the  correct aperture of the diaphragm. Suggested apertures for each objective are as follows: OBJECTIVE  APERTURE OF IRIS  4X  From fully closed to 1/8 open.  10X  From 1/8 to 1/4  40X  From 1/4 to 1/2  100X  From 1/2 to 3/4  -6-  D. Adjust diopter for differences in eyesight. (Only for models B1-220 and B1-223)  E. Adjusting the aperture of the diaphragm.  C. Focusing the microscope.  B. Interpupillary adjustment of head. (Only for models B1-220 and B1-223) 