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FireGryphon
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What's a good microscope?

Wed Sep 02, 2015 7:16 pm

This arguably belongs in the Hardware forum since many microscopes can be hooked up to computers. :-D

I teach elementary school science and I would like to buy a microscope or two for teaching purposes. I currently have one that has an LCD display instead of an eyepiece, but the image is not clear enough to use higher magnifications, and the lighting of the sample is too dark. My students are initially amazed by it, but it has very limited instructional potential, and I'd like to upgrade to a microscope with better optics.

I've read about microscopes on microscopes.com from $70 all the way up into the thousands of dollars, but without seeing them in person and trying them I have no context for what is important on a spec list.

Any advice from the science-inclined gerbils among us?
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DrJ
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Re: What's a good microscope?

Wed Sep 02, 2015 7:52 pm

Get a good used microscope fitted with a trinocular port and attach a digital camera through a relay lens. Most of my 'scopes are by Leitz (three of them) but Nikon, Olympus and Reichert/American Optical are fine too. Some of the recent Russian and Chinese ones are OK, but you have to be more careful .

Honestly, optics have not changed that much over the last 50 years, so an old one that has been well cared for is fine for all but the most demanding purposes.
 
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Re: What's a good microscope?

Wed Sep 02, 2015 8:16 pm

As a former science student, the things I looked for in a lab scope were 1) good bright light from below the sample*, and 2) the adjustment mechanisms not being excessively worn and/or loose. As long as you've got good glass along with those, the rest is gravy.



* in my experience there's never enough ambient light for just a mirror to work well, at least not in school science labs.
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DrJ
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Re: What's a good microscope?

Wed Sep 02, 2015 8:25 pm

bthylafh wrote:
the things I looked for in a lab scope were 1) good bright light from below the sample*, and 2) the adjustment mechanisms not being excessively worn and/or loose. As long as you've got good glass along with those, the rest is gravy.


Yikes. My main 'scope is an inverted epifluorescence Leitz, which we also use for general bright-field use (it also has phase contast). In the latter case the illumination is from the top, though the sample is interrogated from the bottom. For epifluorescence use of course both are from the bottom.

Also, in my experience old 'scopes usually have their grease dry out and have their focusing mechanisms get stiff. My original Ortholux is an example -- it works fine, but it takes a lot of physical effort to focus it.
 
DrJ
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Re: What's a good microscope?

Wed Sep 02, 2015 8:37 pm

You know, it occurs to me that I have a couple of spare upright 'scopes. Both are Chinese but OK; one has a USB video camera attached. Both are like new -- one was demoed at Berkeley but returned in fine condition. Let me know if you are interested, and we can connect off-line.
 
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Re: What's a good microscope?

Wed Sep 02, 2015 9:13 pm

To start with, I have effectively no knowledge about microscopes.

With that massive caveat out of the way, I was given an Aven zipScope as a present a few years back, and it's really cool. Dead simple to focus, good LED light ring for uniform lighting, and actually useful (used it to do repairs on annoyingly small bent pins on a laptop motherboard last year). It runs off USB power when you plug it in and it's seen as a standard USB video source, so I just turn on VLC and use the entire screen as the microscope viewing display. Plus, that also gives me the option of recording anything particularly interesting.

It's not terribly expensive, the picture is clear (here are some pixels on my Nexus 7 at maximum magnification), and I think it'd be pretty suitable for showing a class of elementary school kids what various everyday things look like when you magnify them.
 
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Re: What's a good microscope?

Wed Sep 02, 2015 9:20 pm

That's pretty similar to the old Intel Play Microscope (QX3) that also is a good way to start, though yours uses incident irradiation. It is not that good a microscope, but it can be useful.
 
DrJ
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Re: What's a good microscope?

Thu Sep 03, 2015 11:52 am

Let's start at the beginning: what do you wish to observe with the microscope?

If you want to look at things like coins or bugs or other things that do not transmit light, you will need you light source and objectives on the same side. If your samples transmit light, like "pond scum," you can use a traditional microscope, whether it is upright or inverted.

How much magnification do you need? We rarely use an objective with greater than 20X magnification -- 10X is the most common for us. Combined with the tube factor of 1.5X and the eyepiece magnification of 10X, that gives a total magnification of 150X for the 10X objective. That will allow you to see features on the order of 10s of micrometers. Is that enough or too much?

Do you need anything other than a brightfield image? You also can get darkfield, phase contrast, and differential interference contrast. My guess is that a simple brightfield 'scope is all you will need.

Do you need light wavelengths other than the visible? Unlikely for your kids, but UV (for fluorescence) and infrared sources also are available.

How much resolution do you need in the digital image? Do you need videos? FWIW, most of our images are captured on an old consumer 3 MP Nikon, and it is plenty good enough for what we do (though it struggles with fluorescence images -- too much dark noise).

My guess is that a simple stereo microscope will suffice. They are easy to use, rugged, provide magnification up to about 100X, inexpensive ring lights are available (~$40), often have a trinocular port for a camera (either still or video) and are available very inexpensively on the used market. I bought one from University salvage for about $150 (American Optical), and it is fine.
 
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Re: What's a good microscope?

Tue Sep 08, 2015 5:57 am

Thanks for the replies, everyone.

bthylafh: Thanks, I definitely want a scope with its own light source.

Chuckaluphagus: That looks like a cool device, and I may end up getting one, but I'd like a microscope with much larger magnification as well. I'll keep this one in mind.

DrJ: that's a lot of options. First of all, I can't seem to find a Leitz or Nikon scope for less than $10,000, but maybe I'm just looking in the wrong places... To your latest post with all of the questions about features: is a scope that does all of these things -- light source on both sides of the stage, digital camera, UV/IR -- affordable? Coming into this the multiple light source is most important, followed closely by the digital camera (which should be as high-res as possible). I hadn't thought about alternate light frequency sources, but now that you mention it, I want it. :) Of course, the most important things are clarity and durability, so the kids can actually see what they're looking at and won't be able to break it when they raise or lower things too much, or spill something, or knock it around a bit. Can you suggest a microscope that does this?

I am also interested in your previous microscope offer. PM with details?

Thanks!
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Re: What's a good microscope?

Tue Sep 08, 2015 7:28 am

You might try asking here: https://www.reddit.com/r/microscopy
 
llisandro
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Re: What's a good microscope?

Tue Sep 08, 2015 9:08 am

What's your budget? "Real" fluorescence is expensive on a real microscope (expensive light source, expensive filters). I'm with DrJ- buying used is probably a good idea. We've bought from places like DoveBid before (scientific equipment liquidation services) with good results- they come with a short warranty. Haven't used them since they got bought by another company, but they were great before. I've heard good things about those AmScopes on Amazon but never used one myself.

On our mammalian cell culture scope we've got an olympus DP-21 cooled CCD system- it was $5k new for the camera and the computer to run it. I conenct to the side-port on our Olympus IX51, but I'm almost positive you could go through the eyepiece instead (cheaper scope won't have a side-port). On ebay it seems the controller units (it's actually a full tiny pc) are going for about $500, and cameras are ~$1500. Our model is marketed as for brightfield only, but it actually works really well for fluorescent samples, provided they are of decent brightness. The biggest advantage of these CCDs is the ability to control exposure time, plus the dark noise as mentioned. But if you could get the camera part for cheap enough, this is an entire computer system for taking publication-quality images and videos. You need an LCD monitor, a flash drive to stick into the computer to saves files, plus a light source (pricey).

More interestingly, these days there are a lot of papers/projects from big microscopy labs with instructions to roll your own- arduino-based, LED excitation, etc, and most importantly, using your smartphone or a cheap CMOS as the detector. These drastically cut down on the cost versus a traditional microscope, which is sold at grant money pricing (basically add a zero).

- the CellScope is awesome: http://cellscope.berkeley.edu/ (http://journals.plos.org/plosone/articl ... ne.0096906). Honestly, I'd go for this.
- http://jla.sagepub.com/content/15/5/355.full
- http://wormlab.rice.edu/LED/ (details here: http://www.wormbook.org/wbg/volumes/vol ... mber-1.pdf)- here you can rig a simple stereoscope for fluorescence.
- thingiverse has a bunch of 3D printable mounts to take images through the eyepiece with a smartphone instead of buying a point-and-shoot.
- imageJ and micro-manager are free, research-grade software packages for image analysis and instrument control.

- something like one of those could be a fun project that could span shop class, physics, bio, etc!


Also, if you're anywhere near a research university with an imaging facility, they love doing high school outreach!

edit:typo
 
DrJ
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Re: What's a good microscope?

Tue Sep 08, 2015 11:38 am

You really do have to answer the question on what you are going to do with the microscope. Namely, what samples do you want to look at? A single microscope that does "everything" (and it won't, really) will be terribly expensive. FWIW, research-grade fluorescence microscopes *start* at $50K new. Those are German or Japanese; the Russian, Chinese and others are considerably less expensive but not nearly the quality.

But there is no way you need such a beast for school kids.

There are many sources for used equipment. I have had good luck with University surplus, and that has the advantage that you can look at and use what you intend to purchase. And don't spend too much on your first 'scope -- use the first one to learn. My first one was a '50s vintage upright Leitz Ortholux with a trinocular port that I bought for $100. The objectives were fine, though the condenser was not the right one. So I replaced that and also got a phase contrast one (eBay for both) and it works pretty well. The focusing mechanism is a bit stiff, but otherwise it is fine.

I think you are too focused on hardware, and not enough on how you intend to use it. You have to answer that first.
 
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Re: What's a good microscope?

Tue Sep 08, 2015 7:07 pm

Sometimes Geology departments upgrade their optical mineralogy / petrology teaching microscopes and dump the old ones. You can find used ones for any where from nearly free to ~$2500.
Here is a link to student scopes from Zeiss.
http://www.zeiss.com/microscopy/en_us/p ... .html#shop
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Re: What's a good microscope?

Tue Sep 08, 2015 9:19 pm

I intend to use the microscope as a learning tool for elementary school kids. I want them to be able to look at prepared slides, and look at things they collect, under the microscope at high magnification. Connection to a computer or a digital camera are bonuses, but I don't care about that if the optical quality is poor; I currently have a microscope that claims to have a pretty high magnification and has a fancy LCD display, but the samples I look at are either too dark to make out detail, too blurry (with optical artifacts) to see any detail, or both.

So, optical quality is really important. Build quality is, too, because even the best-meaning elementary school kids are still elementary school kids, and they'll be a bit hard on the hardware. A USB or digital hookup would be great so I could show things to the class or capture a specimen for later study. If using alternate light sources (like UV) is just a matter of swapping in a different LED, I'd like that capability, but I honestly hadn't thought of it until it was mentioned here.
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DrJ
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Re: What's a good microscope?

Tue Sep 08, 2015 10:55 pm

That's a good start. Can you see through the things you want to see on the prepared slides? FWIW, my experience with my granddaughter when she was that age is that she wanted to look at coins, bugs, leaves and other solid objects with which she was familiar. She had little interest in the various and sundry organisms that populate stagnant water, or other things of more classical biological interest. You could see through paper well enough, but most of the samples she wanted to look at did not do well on a traditional microscope. (And yes, that was the old Ortholux.)

The reason this matters is that most conventional microscope, whether upright or inverted, use light that illuminates the sample from the opposite side as the objective and the rest of the optical system. If your sample is opaque, you don't see much. What you see is really dark, and lacking in all detail. To look at opaque samples, you need an incident-light microscope, such as the stereoscopes I mentioned earlier, or the metallurgical ones that another poster mentioned. Yes, you can do incident-light illumination with a traditional biological microscope, but it is much less common.

You mention that you have tried a microscope without good results. What did you use? Could you post a representative image? What sorts of magnifications did you use?

Fluorescence is much more than adding a different light source. Usually fluorescence is measured with incident light (hence epifluorescence) and you have to add a filter to remove the incident illumination from the fluorescence signal (the Stokes shift). That's accomplished with filter cubes, and you need one for each family of fluorophores you are imaging. Traditionally these are for cell stains, and include FITC, TRITC and DAPI. These days the fluorophore manufacturers design them to use the traditional wavelengths excited by a high-pressure mercury lamp; lasers too are used for other frequencies. You also have to make sure your sample fluoresces -- that usually is by an added fluorophore, but some things fluoresce naturally.

There also is the issue of working distance. That is how far the sample is from you objective; the larger the working distance, the farther your objective is from your sample. A large one is good for kids, as they are less prone to crash your expensive objectives into the sample. Stereoscopes have a very large working distance, and so are good for this. Metallurgical scopes are pretty good in this regard too.

The downside of a large working distance is that the light-gathering ability of the objective (the numerical aperture, or NA) goes down. That's basic physics -- if your gathering device is farther away, it sees a smaller portion of an irradiated sphere. That is also why very high magnifications (say, an objective with a magnification that exceeds 40x) requires an immersion oil to get the refractive indices of your cover slip, the air gap (not there with immersion oil) and the objective to work out properly. These also are things a kid should not do, at least not initially. I'll remind you that a 40x objective is 40x1.5x10 or about 600x total magnification, at least on the 'scopes I have.

I'll also caution you about camera resolution. Most good microscope cameras only have a resolution of 1 MP or so, and that is plenty good enough for a cover on Science. What they do have, though, is a large dynamic range and low black noise. Those it turns out are much more important than raw pixels.

Finally, I think you might be surprised on how little magnification you actually need for your samples. When I got started with them, I too thought that very high magnification was important. For what I ended up doing, it just wasn't.

I'd encourage you to look at a Stereoscope first. They have very long working distances and incident-light illumination (for opaque samples), and don't have an objective turret that you have to change. Instead, they have a continuous zoom to take the magnification from about 7x to 50x. They are very rugged, and many are available on the used market. When you want a picture, you can remove an eyepiece and install your camera -- we do this routinely. Inexpensive ring lights are available for sample illumination. Yes, their magnification is limited, but I bet you it is good enough for what you intend.

Most jewelers, machine shops and gun shops have them, in addition to the usual scientific places like mine. You should be able to find an example without too much work. If that is not good enough, then we can consider alternatives.
 
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Re: What's a good microscope?

Wed Sep 09, 2015 6:43 am

DrJ wrote:
Can you see through the things you want to see on the prepared slides? ... To look at opaque samples, you need an incident-light microscope, such as the stereoscopes I mentioned earlier, or the metallurgical ones that another poster mentioned. Yes, you can do incident-light illumination with a traditional biological microscope, but it is much less common.


Yes, I definitely want a stereoscope, since I'm sure the kids will want to look at things they can find. I also want a traditional microscope to look at more common prepared slides.


You mention that you have tried a microscope without good results. What did you use? Could you post a representative image? What sorts of magnifications did you use?


The microscope I used was both lit from the bottom and had a little arm with an LED to light the sample from above, though the LED arm was ineffective. I can unbox it today and see the company and model, but I won't be able to pull an image for lack of the right memory card -- the picture was poor, so I decided it wasn't worth it to buy a card.


Fluorescence is much more than adding a different light source. ... You also have to make sure your sample fluoresces -- that usually is by an added fluorophore, but some things fluoresce naturally.


The idea is intriguing, but if scopes that do this are so expensive, it's not on my list of features any more.


There also is the issue of working distance... Metallurgical scopes are pretty good in this regard too.


A large working distance is probably a good idea.


The downside of a large working distance is that ... I'll also caution you about camera resolution. Finally, I think you might be surprised on how little magnification you actually need for your samples.


Noted.

I'd encourage you to look at a Stereoscope first. They have very long working distances and incident-light illumination (for opaque samples), and don't have an objective turret that you have to change. Instead, they have a continuous zoom to take the magnification from about 7x to 50x. They are very rugged, and many are available on the used market. When you want a picture, you can remove an eyepiece and install your camera -- we do this routinely. Inexpensive ring lights are available for sample illumination. Yes, their magnification is limited, but I bet you it is good enough for what you intend.

Most jewelers, machine shops and gun shops have them, in addition to the usual scientific places like mine. You should be able to find an example without too much work. If that is not good enough, then we can consider alternatives.


This is a good starting point, thanks. I have a type of scope and some possible places to find 'em, but I still feel a bit in the dark about companies and other specs... let's see what I can find!
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DrJ
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Re: What's a good microscope?

Wed Sep 09, 2015 11:40 am

Here's a helpful link that describes the various microscope types and manufacturers, with an emphasis on the used market:

http://www.ebay.com/gds/Buying-Microsco ... 695/g.html

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