The_Simpsons - 11-12-2005 at 12:25
im 16 and im developing a huge interest in microbiology, and im thinking in buying a microscope, but they can be quite expensive, my question is: how
strong microscope do you need to be able to see bacteria and unicelluar eukaryotes(sp?). i know the size can vary greatly, but im mostly interested in
the bacillus-type. so im looking for something affordable but that lives up for my needs.
Chris The Great - 11-12-2005 at 15:00
I have limited experience with microscopes, but have had a very nice (and expensive one) for some time.
I learned that quality makes a HUGE difference. I had an old microscope from a kit from a science store before it and although it went up to 900x you
could barely see anything, focusing was nearly impossible etc. I got a new one for christmas, unsure of the price (looks expensive) and it madea HUGE
difference. You can see cells and such and it is really cool. The cheap one barely saw anything at all.
So you'll probably want to look for something used. But do not just buy a cheapy one because it is cheap, there is a reason it is cheap and you
probably won't see anything you are looking for.
I am not sure of the magnification you will need. Just that magnification means nothing if the lenses suck.
chemoleo - 12-12-2005 at 11:08
I agree with Chris.
Regarding microscopy of bacteria - that will always be difficult. You'll never get to see bacteria at as high a resolution as mammalian cells, simply
because they are much smaller.
At maximum resolution (500x), using a professional microscope, bacteria were barely visible blobs, while insect cells were as big as your thumbnail at
armslength way.
Even at 1000 x, they'd be just twice as big, and still tiny blobs.
Polarisers in the microscope help btw, they increase definition, and make cells more visible.
Other than that, you'd need a fair collection of stains, you could for instance stain them to find out whether they are gram +ve or -ve.
REally, if you want to study bacteria properly, you'd need an electron microscope... which is not quite in anyone's budget, agreed 
denatured - 11-3-2006 at 12:56
We work in microbiology lab using a light microscope with the immersed oil lens and external light source and we could identify the bacteria clearly
but all the slides is stained with methylene blue , voxin etc.
You could get a one like those we use by 80-100USD
There another type i saw while we were preparing mitosis(in plants Allium Cepa) slides with internal light and very good image sharpness but also is
very expensive about 800USD.....
I don't know why electron scanning microscopy is SO expensive ... i looked up for the prices and i have found a used one by 50,000USD ????????
Zeiss
Niels Bohr - 21-3-2006 at 15:45
I have no experience in Zeiss microscopes but after much googling I think thats what you want to buy.
Baytronix
MadHatter - 22-3-2006 at 02:38
I bought this stereoscopic microscope on eBay for $600 plus shipping. With methylene blue or
any other decent stain, I can see the metal particles I'm looking at. This is at 1600x using
the oil immersed lens. Not cheap but definitely serves my needs. An electron microscope is
the only way I could see it better, but like most people, out of my price range.
HELP ! I am in search of a microscope !
Niels Bohr - 22-3-2006 at 11:18
This article was originally published in Dutch, in the magazine : “Natura”
by Henri Schlötz
Almost every naturalist or nature-lover owns a camera or a pair of binoculars, but very few people have microscopes at their disposal.
Both binoculars and microscopes enlarge objects we want to study more carefully, but microscopes make us enter an unknown world and what’s more,
they can be used in the evening or when the weather outside is cold and unpleasant.
There are two sorts of microscopes. Stereomicroscopes, also called binoculars and the “ordinary” microscopes with larger magnification. There are
models for incident light and for transmitted illumination. Some microscopes combine both methods. Incident-light microscopes are meant -for
untransparent objects, those for transmitted-light purposes are made for studying transparent objects. Stereo-microscopes are easy to handle. Just put
an insect or a lichen under the objective and there it is. This article is about transmitted-light microscopes, often for biological purposes.
SECOND HAND
It is a misunderstanding that a microscope would cost you a fortune. Prices of microscopes are comparable to those of single-lens-reflex-cameras. Of
course for new ones of the major German or Japanese brands we have to slaughter our piggy-banks. But as microscopes are almost always used inside and
maintained by experts, they do not wear when used properly. And we can certainly be very happy with a second-hand one. In most laboratories there are
beautiful instruments that will be written-off after some years and than sold for payable money. In Holland there are a few retailers that sell
second-hand microscopes of all kinds at reasonable prices and guaranteed.
LEADING-BRANDS
By now, it will be clear to you that I think you’d better buy a used, but good instrument of a leading brand than a cheap new one. One of the
reasons however is that cheap brands can be good, but one cannot be sure that those microscopes can be repaired in a few years time and that
spare-parts and/or accessories will be available. Although we do not consider it important, when buying a microscope, that there are sufficient
accessories available on the market, in due course we often change our minds. Older models of leading brands are often made of better quality (less
synthetic) materials and they have sold better, so again : more spare parts and accessories.
ZEISS – STANDARD
Zeiss have been building microscopes for more than 60 years according to a certain standard and that makes this brand more suitable for
amateur-microscopists. This means that almost all available accessories fit the Zeiss-standard microscopes. It is certainly true that other leading
brands are well matched. In 1980 the “Zeiss-norm” became the overall standard. (DIN). ( Long-objectives and a tube-length of 160 mm.) Different
Zeiss-objectives can be used in the same nose-piece of different Zeiss models. Until 1980, the German factory Leitz used its own standard. A
tube-length of 170 mm. Objectives of this brand are not all compatible because there are long and short objectives both meant for 170 mm. tubes but
not interchangeable. Olympus did the same thing. You should keep this in mind when considering to buy an instrument of these brands. Also when you
think of buying a microscope of an obscure make, sometimes made according to out-of-date standards, do not think of buying missing parts later on.
SCRATCHES
At what things should you pay attention when buying a used microscope? All moving parts should run smoothly and without tolerance. Front lenses of
objectives must not show scratches. You can only see this using a magnifying glass. When looking, using a pocket-lens, through the rear-end of an
objective you can see whether the kit that glues the lens parts together is still in tact. In case you see little cracks, spots or lines : don’t buy
the objective; Scratches disturb the image.
SQUINT
When you buy a binocular microscope, the image should be clear, especially when using larger magnifications. Both tubes must not be squint, as we call
this, which means that both separate tubes and lenses form slightly different images in your eyes and this can cause a headache. A binocular being
squint or not can be checked in using a special eyepiece containing a graticule preferably one with cross-lines. These graticules are not expensive
and very handy when studying diatoms.Put an object under the objectives, focus on this object and see that a particular part of the object is under
the spot where the lines cross. Now you remove the graticule and put it in the other eyepiece. The same part of the object should appear under the
cross-lines. If not, the microscope is squint.
THE CRUSHED FLY
Handling a microscope is as easy as using a single-lens-reflex camera, but certain things should be kept in mind. Once the owner of a beautiful
microscope was disappointed and liked to sell the instrument because nothing could be seen through it. When I asked what he had done, he told me that
he had caught a fly, put it under the microscope and had tried to get a sharp image using the objective with the largest magnification. He had moved
the objective downwards until he crushed the fly. He put the microscope away as unusable. I am afraid that many microscopes share the same fate.
THE ILLUMINATING PATH
How does a microscope work ?
A microscope is an instrument containing two magnifying glasses. The first glass magnifies a transparent object and the second glass magnifies this
image again. When looking at the illuminating path of the light through the instrument (see drawing) one will understand how the microscope works.
Light comes from a lamp or the mirror, goes through the transparent object (see the little arrow pointing to the right) and trough the magnifying
objective, is again magnified by the eyepiece lenses (the upper-arrow pointing to the left) and is then seen by the eye. (See the larger arrow beneath
the left pointing one).
The total magnification can simply be found by multiplying the number on the objective with the number on the eyepiece. An objective of 40x used with
an eyepieces of 10x gives a magnification of 40x10= 400x. The microscopes works according to the principle of the slide projector. The only difference
is that the image is not projected on a screen but on our retina.
RESOLUTION
Largely misunderstood is the importance of the magnification of the microscope. The resolution of lenses, which is the extent to which certain details
appearing next to each other, can be distinguished, is far more important. The well-known toy-microscopes enlarge to a certain extent but the
resolution is disappointing by lack of quality of the lenses.
DIAPHRAGMS
The “ordinary” microscope is a transmitted light microscope. That means that the light goes through the preparation. Underneath the stage, the
preparation-table, there is a condenser; an optical instrument that concentrates the light to a highly lighted circle in the preparation. In the
condenser there is a diaphragm, regulating the angle in which the light comes in and also the contrast. The amount of light should not be regulated by
this diaphragm. In case you do, you spoil the image. Image will get more course and small details disappear. The amount of light ought to be regulated
by filters or by changing the voltage of the lamp. In more extensive microscopes there is another diaphragm in the foot. Nowadays most lenses of
objectives are very well coated and that diminishes the need of the so-called field-diaphragm.
PREPARATIONS
Unless we are interested in a special field, we put anything transparent under the microscope. After a short period of time things become boring and
then we apply ourselves to a more scientific approach. Dirty flower-water, or water from between water- or pond-weeds contains interesting organisms.
One drop is sufficient for hours of pleasure. With a pipette we bring a drop of water on to an micro slide which we subsequently cover with a micro
cover glass or cover slip. When the cover glass floats on the drop, the drop was to big.The overflow of water can be removed with a piece of
filtering-paper.
FOCUSSING AND ADJUSTING
Using a microscope means a constant turning on knobs. Only a small part of the preparation can be seen through the microscope and only a small part is
seen as a sharp image. The total image is formed in your brain. Whilst focussing you will meet special details only hundredth’s of millimetres in
size.
When operating a mirror, turn the plane side to the sky. Never point the mirror at the sun. It will severely damage your eyes. And you should never
use the hollow side of the mirror which was only used in the days of the oil lamp to concentrate the rays of light. When you use non-adjustable
electric lighting, you may regulate the lighting by neutral grey filters or by two polarising filters. After adjusting the lighting, put an object on
an object glass and put this on the stage. Start with a smaller magnification. This has the advantage that you will see an image almost instantly and
because of the large distance between objective and object you can hardly damage anything. After that you put the condenser in the highest position
and open the condenser diaphragm entirely. The stage is also fixed in the highest position (or your turn the tube down, depending on the construction
of your instrument). You should adjust the lighting according to the light that surrounds you. That is more agreeable when you would like to look up
something, in a book for instance, whilst using your microscope.
FINE-FOCUSSING
Fine-focussing is done in using the calibrated mechanical stage. The object is pushed by this stage into the narrow light-beam and using a lower
magnifica-tion objective, you adjust your microscope only roughly. When this produces a sharp image, you turn the objective revolver until an
objective of larger magnification is a placed above your preparation. Now is the time for fine-focussing, often by a smaller knob, mostly on both
sides of the microscope. When your microscope is a binocular one, you should stare into the eyepieces. Don’t look for a sharp image, but adjust the
pupil distance so, that you will see the same image with both eyes. After that you may focus for a sharp image by turning one of the knobs, like you
would do with a transmitted light instrument.
To obtain a correct proportion between sharpness and contrast you remove one of the eyepieces and look into the tube. Than you close the condenser
diaphragm for about 30 %. That means that 30% of the luminous point is covered.
(This method is advised by Carl Zeiss).
COATING
Most laboratory microscopes have lighting including a diaphragm incorporated in the foot. This is easier to operate than a mirror. There is no need
for adjusting the mirror to the light source, because the light is always in the same place. Objectives are coated nowadays, but this does not mean
that there should be no reason to adjust your Köhler-lighting properly, especially at magnification of more than 10x. Chose the right objective, the
one you would like to use. Close the lighting diaphragm so that the rim could just be seen through you eyepiece. Then move your condenser upwards and
downwards until that rim is seen as a sharp image. By using the centre screws of the condenser you can put the clear spot right in the middle of the
shadow of the diaphragm. Now open the diaphragm again so far that the rim has just disappeared from your image field. After this your microscope
should be perfectly adjusted.
EXPERIENCE
The above seems to be rather complicated, but after a few times practising, you will get sufficient experience. You will see immediately when your
microscope is not properly adjusted. Adjusting your condenser is very important because only then the optical quality of your objectives will show
full advantage. It is said that using your microscope is like riding a bike. You will never loose your skill.
We wish you lots of success with your microscope!
Henri Schlötz is a social scientist and a KNNV- member. He developed an interest in using the microscope when on secondary school, his
biology-teacher showed him the circulation of the blood in the tail of a tadpole.
THE CONSTRUCTION OF THE MICROSCOPE
To understand how the microscope works, we should know the various parts and what they are used for.
From top to bottom we recognise :
1) The eyepiece, through which we observe the image.
2) The binocular tube, with which we can compensate the differences between our eyes.
3) The clamping-screw to secure the tube.
4) The nose-piece or objective revolver containing the objectives.
5) The frame-head
6) The frame
7) The stage
8) The condenser with:
9) the opening diaphragm
1o) the knob to put the frontlens beside
11) the centre-screws
12) Filter-ring
13) ring containing moveable auxiliary lens for lower magnifications.
14) Knob(s) for rough and fine focussing.
15) Incorporated lighting.
16) Ring for adjusting of field-diaphragm.
17) Foot.
Although this microscope seems to be very complicated, there is no difference in operating this one or a less complicated instrument.
bron foto: ZEISS STANDARD
Twospoons - 22-3-2006 at 21:30
I've only used low power binocular microscopes (for electronics) but my experience with Zeiss was bad. The eyepieces were extremely hard to use - you
had to position your eyes exactly right. Currently I'm using scopes from both Meiji and Nikon. Both are very user-friendly. The Meiji scopes are
well priced, and good quality.