How to use a microscope

So you just received your first microscope and want to look at some specimens. In this article I want to give you some advice on how to do that. I have also prepared some videos (see below) that I encourage you to watch, because – as the saying goes – a picture says more than a thousand words. Here is a summary of the steps:

  • Choose the right slide: Many microscopes come with a set of prepared slide. Choose one where you can easily see the specimen with your unaided eye. This will also make it easier for you to see the specimen under the microscope. After you have managed to look at the prepared slide, you can always make your own slides later.
  • No prepared slide? If your microscope does not come with prepared slides, then you quickly have to make one yourself. Take a slide, put a drop of water on it. Cut off a small amount of hair (about 5mm long) and put it into the drop of water. They should not overlap too much. Put a cover glass on top. Of water flows out, then remove it with some tissue paper. If there are some air bubbles, then don’t worry for now. Just make sure that the cover glass sticks well on the slide because of the water. The cover glass should not float on the water when you move the slide (use tissue to remove excess water).
  • Adjust the objective: Rotate the 4x low power objective (the one with the red ring) into position. This will make focusing much easier.
  • Lower the stage: Turn the coarse focus knob and lower the stage. This will make it easier to insert the specimen slide.
  • Insert the slide: The label must be on top. This is the side that also has the cover glass. Make sure that the slide is centered properly. The specimen must be right above the hole on the microscope’s stage.
  • Raise the stage: Use the coarse focus knob to raise the stage all the way. Check that it does not crash into the objective (it should not, because you will not be able to turn it higher with the 4x objective in place.)
  • Turn on the microscope: You need to turn on the main switch first. If it does not light up, then you need to turn the light intensity knob (or wheel).
  • Raise the condenser: Some better microscopes have a condenser mounted beneath the stage. Find the knob (on the left side beneath the stage, or a horizontal lever) and raise the condenser all the way up. You should be able to see the condenser go up and down. This is not the lever that controls the diaphragm.
  • Close the diaphragm: This is a lever on the condenser that can be moved left and right. It does not raise and lower the condenser, but opens and closes the diaphragm. Move the lever to the position where the image becomes the darkest. This will also give you the highest contrast and depth of field. If it is too dark, turn up the light.
  • Focus: Now look through the microscope and use the coarse focus knob (the large one) to lower the stage until you see a clear image. Don’t just rotate it back and fourth, but rotate it into one direction. If you do not see a clear image at all, check that the slide is centered.
  • Recenter: This is important. The part that you want to look at more closely should be in the middle.
  • Change magnification: Now you can rotate the next higher objective into position. This is the 10x objective. The objective will be very close to the slide, but do not worry, it will not touch the slide – if it was in focus with the 4x objective. Some beginners are afraid that it will touch the slide and will move the stage down again before changing the objective, but this is wrong.
  • Refocus: Now use the fine focus knob to focus. If you use the coarse focus knob then there is indeed the risk of crashing the objective into the slide and damaging both. If you lose the focus, which can happen easily, then start again with the 4x objective. This is faster and safer than trying to find the focus using a higher magnification.
  • Open the condenser: Experiment with the condenser aperture diaphragm. Open and close it until you get am image that is satisfactory. Different specimens will require a different condenser. Specimens that are low in contrast need to have the condenser closed more.

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