If you enjoy science and like getting hands-on with research and experimentation, you’ll no doubt have to use a microscope at some point.
Then, it’s only a matter of time before you’re hit with a bunch of microscope-related jargon.
Two of the most common specialist terms used in this area are “coarse adjustment” and “fine adjustment”.
They may leave you scratching your brain box at first, but they’re actually very simple, quite intuitive terms that, with a tiny bit of guidance, you’ll pick up in no time.
In this article, I’ll be breaking down precisely what these terms mean and in what sort of scenarios their corresponding actions are required. Sound good? Good; let’s get to it!
What (And Where) Are Coarse And Fine Adjustments?
In this context, the terms coarse and fine refer to the scale of stage adjustment on a microscope.
Simply put, coarse adjustment allows you to move the microscope stage quickly, while fine adjustment refers to moving the stage in a more gentle fashion.
This is done by using the aptly named course and fine adjustment knobs on a microscope, but where exactly are these handy knobs?
Well, they’re not exactly hidden away.
Typically, you’ll find the larger coarse adjustment knob further up the arm of the scope.
The fine adjustment knob will usually be below the larger knob, further away from the viewer, near the base of the scope arm.
Although the fine knob is quite a bit smaller than the coarse adjustment knob, both are perfectly easy to find and use while looking through the microscope.
Some designs make adjustment even easier by utilizing a creation invented by Leonard A. Wilkinson in 1962 known as coaxial control.
This allows for the coarse and fine adjustment knobs to be in line, or rather, on top of one another, facilitating easier, more efficient use.
Ease of use is key here, as it allows you to feel your way around and operate the microscope without having to leave the eyepiece.
That’s all simple enough, right? But your next question may be something to do with the necessity of two controls that, ultimately, do the same thing.
It’s a valid query, but to say they’re doing the same thing isn’t quite right.
You see, when you’re working with high magnification settings, the coarse adjustment knob simply moves far too quickly.
You’ll move it ever so slightly, and boom! Suddenly you’re more out of focus than before. This is where the fine adjuster saves the day.
Conversely, if you’re in quite low magnifications, or you need to move the stage quite a distance to get your observations started, you’ll be turning the fine adjustment knob all day long, whereas the coarse adjuster will have you set up in seconds
This concept of two controls (one macro and one micro) for the control of an individual act with a piece of equipment is by no means limited to microscopes.
It’s a technique used in multiple ways to make a variety of different things more practical to the user.
On certain samplers used by music producers, for instance, there may be discrete coarse and fine adjustment to help them navigate and precision edit the waveforms of an audio file.
Oftentimes on a microscope, fine adjustment knobs will be fitted with some sort of affirmative click system that gives an auditory confirmation to the user as they twist.
While not essential, it does help to add even more control to the situation.
Likewise, to make a coarse adjuster easier to use, it may be fitted with a numerical dial, sort of like the markings on a protractor, as a means to add some precision to the mix, but this is something of a luxury you will typically only find on superior designs.
How Do You Know Which Adjustment To Use?
Thankfully, there are no complex guidelines for using the coarse and fine adjustment knobs.
All we need to do is follow proper microscope use protocols. Don’t sweat it if you’re not sure what these protocols are, as I’ll detail them now.
- Starting out
When you’re first starting your observation, you should always make sure that you’re as zoomed out as possible (using the lowest power objective) and that the stage is as low down as it will go. You can consider this the basic foundation for any viewing session, your blank canvas, if you will.
- Coarse adjustment first
With your new subject slide locked and loaded, and your microscope ready for action, you can now use the coarse adjustment knob to get your specimen focused up in record time.
- Slide adjustments
Now that you can see your specimen with acuity, your next job is to make sure the slide is correctly centered on the stage. To do this, you can either use the transitional X/Y knobs or use your fingers to adjust it manually.
- Increase magnification
Okay, so you can see your specimen clearly, it’s nice and centered; next on the agenda is to increase the magnification. Don’t zoom up to the most advanced lens straight away. Simply jump up to the next objective power.
- Fine adjustment
After zooming in, you’ll likely lose most of your focus, so now’s the time to grab that fine adjustment knob and regain some clarity.
- Rinse and repeat
You’re done with the coarse adjustment at this stage, but for every strength of magnification you go up, you’ll need to readjust with the fine adjustment knob, otherwise, all you’ll be seeing are blobs and blurs.
Do You Turn The Knobs Clockwise Or Counterclockwise?
Which way you turn the adjustment knobs depends on the type of microscope you’re using.
Usually, if the eyepiece is not facing the microscope arm, then turning the knob towards you will lower the stage, and turning the knob away will raise the stage.
This means that – looking from the side – a clockwise motion will raise your stage, while an anticlockwise motion will lower the stage.
If you’re ever unsure of which direction to turn the knobs, I’d suggest just taking a moment to experiment with them, then noting down which direction achieves which action.
How Do You Fine-Tune Adjustment Knob Tension?
You may notice that there’s an extra adjuster on your microscope. This is usually a tension adjustment knob, and it allows you to make your coarse and fine adjustment knobs either more stiff or loose.
Some tension adjustment knobs can be dialed in manually, while others require the use of a small tool.
Regardless of whether your tension adjustment is a manual or tool-oriented design, it will look like a wheel behind the adjustment knobs themselves.
Adjusting one way will stiffen up your adjustment knobs to increase precision and prevent accidental focus loss.
Adjusting the other way will loosen things up, making your adjustment knobs easier (and quicker) to turn.
Final Thoughts
You made a wise choice coming here today, as knowing the difference between coarse and fine adjustment knobs is an integral part of microscope use 101.
To sum up, The coarse adjustment knob is for quick moving of the stage to find a focus when you’re just establishing your observation.
The fine adjustment knob allows you to gain focus later on in higher magnification settings.
Now you know what these knobs do and how to use them, you’re free to satisfy your scientific curiosity to your heart’s content!
Ever since I was a little girl, I have been fascinated by science. Every holiday I would ask for the newest science kit, and spend weeks learning with it.
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