Microscope Basics: Purchasing and Focusing a Microscope

[endif]-- When purchasing a compound light microscope, there are a few things to take into consideration:

1) As with any optical equipment, better quality will cost more. A higher priced microscope will provide sharper images and detailed structures will be easier to find and identify. Consider how many children will be using the microscope and your child’s interests. If they are interested in a science career, they may use the microscope more than just for this one course.

2) My personal preference is a monocular scope (one eyepiece). Some students may prefer a binocular scope, but it takes a little getting used to. Scientists that work with microscopes for several hours a day use binocular scopes to prevent eye fatigue, but your students won’t be using the microscope that long, so either is fine. The recommended microscopes that follow are all monocular.

3) A compound light microscope uses two lenses to magnify an image. One lens is in the eyepiece and one objective lens is used to provide additional magnification. The objective lenses rotate into place when viewing the slide. The total magnification level is determined by multiplying the eyepiece magnification (usually 10x) by the objective lens magnification. Make sure that the total magnification of any microscope you choose is at least 400x. There is no need for magnification above 1000x, as the differences become barely noticeable beyond that point.

4) Any good compound light microscope will have 2 focusing knobs. The coarse adjustment knob moves the stage and brings the image into focus. The fine focus knob provides small changes that allow to students to see different dimensions of the specimen once the object is in focus. A fine focus knob is essential for bringing cellular structures into view.

Other handy things to have:

-Stage clips keep slides in place. This is helpful, but not essential. Just don’t bump the microscope once you get it focused!

-An X-Y slide holder allows tiny movements left and right. This is very helpful on high power, but students can simply move the slide with their hands. It may be frustrating at first, however, because even small movements can seem large under medium or high power.

-Most microscopes come with a diaphragm and condenser to adjust the amount of light coming through the slide. This allows students to adjust when an image is too washed out.

-A camera can be mounted on many microscopes. If you know you’ll be taking pictures of specimens, look into the quality of the digital image when choosing a camera.

I've provided some recommendations below. I am not an affiliate of any of these companies, so feel free to use the information as you'd like. I've also provided a video below for a review of this information, as well as tips on focusing your microscope once you've purchased it!

1) The works: Sonlight Ultra Microscope $260.00

Features: 400x magnification, solid construction, stage clips and X-Y slide holder, LED bulb

2) Middle of the road: AmScope M500 $120.00

Features: 400x traditional magnification + 1000x oil immersion for viewing bacteria (not essential for most Biology courses), stage clips, traditional tungsten bulb, color filters for eyepiece

3) Basic model: AmScope M150C $85.00

Features: 1000x magnification, stage clips, LED bulb