The National Optical and Scientific Instruments Model 157 Compound Microscope is designed for the classroom, with a number of teach-preferred elements. First and foremost would be the 157's magnification which is 40x, 100x, 400x, and 1000x. Allowing students (and teachers alike!) to experience these magnification are the four DIN standard, achromatic, parfocalled, parcentered, and color-coded objectives in 4x, 10x, 40xR, and 100xR. Of course, also essential to the microscope's operation would be the 10x widefield eyepieces.
The Model 157 is illuminated by a built-in 5W fluorescent light. This light virtually gives off no base heat and is rated with a life of 10,000 hours. An on/off switch on the base allows for easy control, while the grounded 3-wire electrical system ensures safety and reliability.
When it comes to focusing, the microscope is both durable and easy for students to use. The slip clutch prevents damage, while the tension adjustment eliminates stage drift. The stage can be moved up or down, and the eyepiece and body remain fixed in place. A safety rack prevents damage to slides and the objective lens.