Tuesday, January 10, 2017

Comparison of inexpensive digital microscopes, part 1

I frequently find myself in need to a digital picture of something really tiny. Sometimes it's halftone printing dots or the pixels on a computer monitor. Sometimes, I just would like to have a closeup picture of an interesting specimen of hemiptera. After all, I'm a blogger who often writes about scientifical stuff. And since I make about $20 per year on this blog, my budget for toys to support this addiction of mine is ironically so tiny that it would require an expensive microscope just to see.

Me, looking for my next paycheck

Needless to say, I have long been on the lookout for an inexpensive microscope. In this blog post, I have a look at an inexpensive USB microscope from Celestron. In the next blog, I will look at a very inexpensive lens that snaps onto your cell phone. (Spoiler alert) In the third installment, I will look at my pick, a new inexpensive and very impressive USB microscope from Opti-Tekscope.

My first USB microscope

In 2010, I bought a Celestron 44302 1.3 MP for $56. I see that Amazon now lists it for $50, but that would not be a good bargain. The updated microscope, with a 2.0 MP camera, sells for $38. But if you happen to want the more expensive, lower quality one, I would suggest jumping right on it. When I checked, there were only seven left.

My old buddy, caught in a moment of leisure

This is a pretty cool toy. Let's see what it can do!

Low magnification image

I decided that I was going to get my wife something from the Fabulous Furs catalog. This first picture that I took with the Celestron microscope shows a woman wearing a parka thingie. This is what I got my wife from the catalog. I didn't get her the parka, of course. I got her a microscope image of a picture from the catalog. Her very own .bmp image. She will be very happy with me.

This picture is for my wife

I don't always know what my wife is gonna say when I get her a present, but I think in this case, she won't be all that excited. That's my guess, anyway. Since I have decided that I am gonna get her an image as a present, I better figger out what's wrong, and how to fix it.

The microscope has six LEDs for illumination, as shown in the image below. Since the lights are directly above the surface being viewed, the specular reflection (the light reflected directly from the surface) will bounce right back into the lens. Since specular light does not react with the sample, it provides us with little information about what the sample looks like. All we get are the delightful white splotches that hide the beautiful model.

The Celestron takes a selfie

So, in order to create an image of the catalog that is useful, I tilted the microscope with respect to the magazine. Thus, the annoying specular light bounced off the surface away from the camera, never to be seen again. 

This picture is for my wife

That's a pretty cool image. You can see the rosette patterns of halftone dots in this very sexy model's naked eyes, and this is definitely clearer than I can see the halftones with my own (equally sexy) naked eyes.

Higher resolution image

But there's more. The above image was taken at the lowest magnification available with the Celestron. The image below shows the other extreme. At full magnification, you can clearly see the individual black, magenta, and cyan halftone dots. You can even kinda make out the yellow halftone dots.

I suspect that my wife may not want this
high resolution image of a halftone representation
of a model's eye 

Another thing I like taking high resolution pictures of is computer displays. We all have our hobbies, right? Below are two Celestron images of the Wikipedia icon on my KindleFire.

Really taking a close look at Wikipedia

You can see bright spots in the four corners of the low magnification image. These are the reflections of the microscope's LEDs. There is no provision in this version of the microscope to turn off the illumination. As we have seen for flat surfaces this is a problem, and it is definitely a problem if we wish to use the microscope to look at emissive stuff like computer displays. (This has been fixed in the current version.)

I disabled the LED illumination of my older vintage Celestron with a delicate swing of a sledgehammer in order to capture the higher magnification image at the right. Here we can start to see what I was looking for - the individual pixels of the display. Below I show a cropped and magnified version of the image. In this image we can tell that the Kindle display has pixels that are rectangular, and are either red, green, or blue. Such an image is incredibly useful for someone who is trying to explain color, but the blue pixels are faint, rather hard to make out.

Kindle pixels

John the Color Science Guy needs to interject a point of interest here. Note that yellow halftone dots were a bit hard to see when the Celestron was pointed at print, and blue pixels were kinda hard to see with the image of the display. Both of these point to a deficiency in the blue channel of the camera. 


Speaking of kvetching about the microscope, I just complained about the blue channel and previously I complained about the inability to turn off the lights on the Celestron microscope.  As I said this has been fixed in the current version, but I'm still gonna kvetch about it cuz I like to kvetch.

One thing that I did not kvetch about in the previous section is that it took me about ten minutes to capture the high magnification image of the Wikipedia icon. Partly this is due my mechanical ineptitude, but I am gonna blame it on the microscope anyway.

The image below shows the two parts of the focusing mechanism.

Focusing the Celestron
On the left, we see the mechanical part of the focus. There are two ball and socket joints held tight with a thumbscrew. Well, the joints have a ball, but the socket is more like two pieces of metal on either side of the ball. By articulating these two joints, we can adjust the working distance, which ultimately drives the magnification of the image. In the image at the left, we see the focus "knob". You use your thumb to rotate the light gray inner cylinder with respect the the darker outer cylinder.

This is a very simple, and one may say, clever, design. But, if I would apply the word clever to this design, I might be more apt to use it in the sense that the rack was a very clever design used during the Inquisition. It is torturous to get a high magnification image into focus. Kvetch kvetch kvetch... 

1) When you bring the scope closer (by bending both of the ball and socket joints, the scope will move to a different position on the sample, so you need to reposition ever time you adjust working distance. Note that I didn't mention the third ball and socket joint on the microscope itself that adjusts the orientation of the microscope itself. This joint also has to be adjusted when you zoom in, since the microscope will change orientation otherwise.

2) If the thumbscrew is tight enough to hold the microscope in place, it will necessarily take a bit of force to adjust, which means that the microscope will probably move while you are zooming in.

3) The focus knob takes a bit of torque to turn, certainly enough torque to move every other part of the microscope. At higher magnification, it doesn't take much motion to completely lose what one was looking at.

4) To top it all off... when the microscope is cantilevered out for a close working distance, the stand will tip forward.


When I bought this microscope several years ago, it was a great investment. Yes, it was tedious to get images, and the images weren't quite the quality that I would have liked, but any other microscope would have been well outside my price range. Just being able to collect images was a great thing.

We shall see that there are other options today.

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