OPERATION  ( cont. ) Model AY11240 Model AY11238 USING THE 5-HOLE DIAPHRAGM COARSE KNOB ADJUSTMENT - Model AY11240 MICROSCOPE USAGE CONSTRUCTION 6 5 7. To clearly see the outline of the specimen, rotate the coarse adjustment knob and lower  the barrel to the space limiter. 8. Rotate the fine adjustment knob until the image is in sharp focus. When using other objectives, rotate the fine focus adjustment until the image is in focus. 6. To clearly see the outline of the specimen, rotate the coarse adjustment knob and lower  the barrel to the space limiter. 7. Rotate the fine adjustment knob until the image is in sharp focus. When using other objectives, rotate the fine focus adjustment until the image is in focus. 1. To obtain the best contrast for observing, match the hole size to the objective that is being used to view the specimen.  2. Each hole has a corresponding number from 1 to 5. 1 is the smallest hole; 5 is the largest hole. Use the following guidelines to match the hole number to the objective that you have selected:  40x objective: Use #5 hole 10x objective: Use #4 or #3 hole 4x objective: Use #2 or #1 hole 1. The coarse adjustment knob has an adjustable heavy-light nut (See Fig.1). 2. To adjust the knob loosen or tighten the nut. NOTE: Adjusting the nut too tight will make focusing difficult. Adjusting the nut too loose will cause the tube to slide. BARSKA Model AY11228 and Model AY11232 are designed for  biological studies such as specimen examination. They can also be used for examining bacteria and for general clinical and medical  studies. Simple design and use is especially useful for school  classroom instruction. BARSKA Model AY11228 is a fixed power stereo microscope. It is  constructed with two optical paths at the same angle. It is  equipped with transmitted illumination and oblique illumination. By using this instrument, the user can observe and enlarge the  right side stereo image. BARSKA Model AY11232 is a zoom stereo  microscope. The object being viewed is enlarged through two  identical sized sets of right and left eye lenses. The zoom provides  different magnification and features an inversion system which  allows the image to be viewed normally and right side up. Fig. 1- Coarse Adjustment Knob Heavy-Light Adjustment Nut Model AY11228 Model AY11232 Diopter Adjustment Diopter Adjustment Prism Cap Prism Cap Eyepiece Stage Lens Stage Vertical  Pole Illumination Controls Rotary Case Illumination Controls Spring  Clips Spring  Clips Focus Knob Focus Knob Magnification Adjustment Knob Focus Knob Tightening Knob Oblique Illuminator Oblique Illuminator Lens  Housing Eyepiece MODEL AY11228/AY11232