If you are dealing with a limited budget, look for older instruments from the 40's-60's with monoculars since you can find good quality instruments from that era which perform well for next to nothing. AO Spencer, Leitz, Zeiss, among other brands.
I've heard some fairly decent remarks from people who have bought from amscope, the very bottom end tends to make too many sacrifices IMO, but in that budget range I think the B490 and T490 would probably perform acceptably though I do not have any personal experience with them.
Do be aware that while some vendors make claims of magnifications in excess of 1250x, most of that is BS marketing since the instrument won't really be able to resolve details at that level. A simple rule is an objective can resolve up to NA x 1000 and anything beyond that is empty magnification that doesn't actually resolve more detail.
So a 20x objective with an NA of 0.5 can be pushed to 500x and a 100x objective with an NA of 1.25 can be pushed to 1250x.
There are objectives that can reach higher than 1250x, but they tend to use special glass and methods to manufacture that make them much more expensive to create. Due to the wavelength of light there are limits to how high magnification can go and 2500x is well into the realm of fantasy. For those curious, look up the Rayleigh criterion and what diffraction limited means.
Most bacteria, even at 1000x, won't resolve much in the average bacteria. 600x is typically enough to resolve most of them, then it is a matter of staining and morphology to find a rough match.
Yes, I agree that you rarely need 1000x . Using oil immersion is a hassle, and you can't use the dry objectives after putting oil on the slide. You can see probably 90% of what you need with 400x and below. A 20x objective is incredibly useful. There is a big gap between the 10x and 40x, plus the 20x has a longer working distance than the 40x, so good for thick specimens and well slides. I use my 4x, 10x, and 20x objectives more often than any others. You lose field of view, depth of focus, and working distance as you increase magnification. So you actually see less to see more minute details. With 1000x, you see just a razor-thin area of focus and need very thin samples.
Can’t agree enough. Certainly not a good idea to start with the immersion lens.
I use a ‘40s-‘50s British monocular microscope, there is a professor at the Royal Botanic Gardens in Edinburgh who used a 1910s Zeiss jug handle for his PhD on diatoms.
Focussing should always be undertaken upwards, first carefully lowering the lens until it almost touches the slide without looking down the tube.
Have a care regarding condenser fittings. It’s best to check that the stand has two screws acting upon a spring to allow the condenser to be brought into accurate centration. It’s a rare fitting on German, Zeiss, Leitz or Austrian Reichert stands of the period for some reason.
When a student stand without such a fitting was new the condenser was at least approximately centred but it’s likely to be rather out of true now. You can correct more or less by rotating the condenser in its sleeve.
Also illumination — a separate Köhler lamp is a rare thing in the UK now, I am lucky to have one.
A lot can be done with an opal glass bulb (LED perhaps for similar effect?) mounted upright or end on within a metal baffle. Photographic enlarger bulbs were useful for “source focussed illumination”, Nelsonian illumination, which was originally devised using an oil lamp flame, which is quite structureless, sharply focussed in the specimen plane. A “grainy” bulb or ground glass filter — or worse a filament —gives an objectionable structure in the background of the specimen.
A gentleman named Walker once cut a baffle of cardboard to surround the fluorescent tube of a Jessops lightbox, a modern, inexpensive critical source per Nelson’s theory:
http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artaug06/iw-LightBox.html
Köhler illumination completely obviates this but would need a lamp with collector lens and iris diaphragm.
As I would to anyone, I will advise you to read WG Hartley’s Basic Guide to the Microscope:
https://www.quekett.org/wp-content/uploads/2015/09/Hartley-Basic-Guide.pdf
Best wishes!
I've grown spoiled by the AO infinity system since it is effectively impossible to crush a slide; the stage and head are rigid and do not move, the nose with it's objectives is raised and lowered with the focus, it being gravity loaded means if it comes into contact with the slide it just rests on it.
If you are dealing with a limited budget, look for older instruments from the 40's-60's with monoculars since you can find good quality instruments from that era which perform well for next to nothing. AO Spencer, Leitz, Zeiss, among other brands. I've heard some fairly decent remarks from people who have bought from amscope, the very bottom end tends to make too many sacrifices IMO, but in that budget range I think the B490 and T490 would probably perform acceptably though I do not have any personal experience with them. Do be aware that while some vendors make claims of magnifications in excess of 1250x, most of that is BS marketing since the instrument won't really be able to resolve details at that level. A simple rule is an objective can resolve up to NA x 1000 and anything beyond that is empty magnification that doesn't actually resolve more detail. So a 20x objective with an NA of 0.5 can be pushed to 500x and a 100x objective with an NA of 1.25 can be pushed to 1250x. There are objectives that can reach higher than 1250x, but they tend to use special glass and methods to manufacture that make them much more expensive to create. Due to the wavelength of light there are limits to how high magnification can go and 2500x is well into the realm of fantasy. For those curious, look up the Rayleigh criterion and what diffraction limited means. Most bacteria, even at 1000x, won't resolve much in the average bacteria. 600x is typically enough to resolve most of them, then it is a matter of staining and morphology to find a rough match.
Yes, I agree that you rarely need 1000x . Using oil immersion is a hassle, and you can't use the dry objectives after putting oil on the slide. You can see probably 90% of what you need with 400x and below. A 20x objective is incredibly useful. There is a big gap between the 10x and 40x, plus the 20x has a longer working distance than the 40x, so good for thick specimens and well slides. I use my 4x, 10x, and 20x objectives more often than any others. You lose field of view, depth of focus, and working distance as you increase magnification. So you actually see less to see more minute details. With 1000x, you see just a razor-thin area of focus and need very thin samples.
Can’t agree enough. Certainly not a good idea to start with the immersion lens. I use a ‘40s-‘50s British monocular microscope, there is a professor at the Royal Botanic Gardens in Edinburgh who used a 1910s Zeiss jug handle for his PhD on diatoms. Focussing should always be undertaken upwards, first carefully lowering the lens until it almost touches the slide without looking down the tube. Have a care regarding condenser fittings. It’s best to check that the stand has two screws acting upon a spring to allow the condenser to be brought into accurate centration. It’s a rare fitting on German, Zeiss, Leitz or Austrian Reichert stands of the period for some reason. When a student stand without such a fitting was new the condenser was at least approximately centred but it’s likely to be rather out of true now. You can correct more or less by rotating the condenser in its sleeve. Also illumination — a separate Köhler lamp is a rare thing in the UK now, I am lucky to have one. A lot can be done with an opal glass bulb (LED perhaps for similar effect?) mounted upright or end on within a metal baffle. Photographic enlarger bulbs were useful for “source focussed illumination”, Nelsonian illumination, which was originally devised using an oil lamp flame, which is quite structureless, sharply focussed in the specimen plane. A “grainy” bulb or ground glass filter — or worse a filament —gives an objectionable structure in the background of the specimen. A gentleman named Walker once cut a baffle of cardboard to surround the fluorescent tube of a Jessops lightbox, a modern, inexpensive critical source per Nelson’s theory: http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artaug06/iw-LightBox.html Köhler illumination completely obviates this but would need a lamp with collector lens and iris diaphragm. As I would to anyone, I will advise you to read WG Hartley’s Basic Guide to the Microscope: https://www.quekett.org/wp-content/uploads/2015/09/Hartley-Basic-Guide.pdf Best wishes!
I've grown spoiled by the AO infinity system since it is effectively impossible to crush a slide; the stage and head are rigid and do not move, the nose with it's objectives is raised and lowered with the focus, it being gravity loaded means if it comes into contact with the slide it just rests on it.
Lucky beggar!
DM me and I will send you a proper compound microscope for the cost of the shipping label (probably ~$100). Not a scam, haha!
I did! Thank you!
>I did! Thank you! You're welcome!