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Why 100x and 430x? ...and fruit fly question

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#1 cpsTN

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Posted 27 May 2013 - 09:09 AM

I have an old, but apparently ubiquitous, Bousch & Lomb microscope. I was reading an older book at the library yesterday and the compound microscope it desribed was mine, saying that the objectives are normally 10x and 40x, but some have 43x. Even the diagram was showing the one I have, so apparently these are common or WERE anyway. On the one I have, the EP is 10x and the Objectives are 10x and 43x, giving powers of 100x and 430x. Why is there such a large power spread here and is this common or only with certain types of microscopes? Also, I have been looking at a fruit fly at 100x and can see the lenses of the compound eye. Is this normal at only 100x or am I seeing something else and just assuming it is the individual lenses? I have noticed that I have to change the focus for different parts. Is this the fault of the scope or is it because the focus is so narrow and because the object is 3-dementional, causing me to have to refocus for different parts? Thank You for your time.

#2 ASTERON

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Posted 27 May 2013 - 10:32 AM

Hello Charles,
Since you did not specify the B&L Model, I cannot comment on your first question. However most Modern microscopes have between 4-5 objectives in the turret allowing for X5, X10, X40 and X100 objectives if the turret is a 5 position one you can add an x20 or X60 to complete the range.
I have also seen other different objectives on the market wit x2, x4, x16 and other exotic magnifications.
It is quite easy to change objectives, so if you need another magnification you can always unscrew one of the objectives and screw another different objective instead.
As for your other (Fruitfly) question, a total magnification of X100 is a very serious mag. and is definitely sufficient to see the lenslets of the insect compound eye. So what you see is real.
You are absolutely correct in assuming that the focus change is due to the usuallyvery limited depth of field of the objective. Your microscope is probably fine but the different distance to different parts of the 3D object is what necessitates the refocusing. If you had used a smaller magnification ( x20-x50) you would probably be able to see more lenslets without having to refocus.
Typically, for smaller mags (X2-x50), it may be better to use a stereozoom binocular microscope, but your microscope may be fine also especially if you get yourself an x4 or x2 objective that is designed for use with your specific microscope (it must be designed for the specific tube lens length of your microscope).
I hope this helps,
Best Regards

#3 Hikari

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Posted 27 May 2013 - 10:54 AM

Well, it is not a large power spread. When you have a limited number of objectives, then a jump from 10x to 43x is not a big jump--only 4x. The scope could also have had 10x and 20x eyepieces, which would have the practically give the microscope an 10x, 20x, 43x, and 86x.

#4 cpsTN

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Posted 27 May 2013 - 07:34 PM

I wasn't thinking about the jump being only 4x more or less.

#5 KennyJ

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Posted 28 May 2013 - 11:25 AM

I understand very little about microscopes, but feel I do understand where Charles is "coming from" with his expressed surprise at the wide difference between the two set magnifications.

A 4x factor between say, a telescope eyepiece yielding 15x and another 60x, doesn't seem so drastic as the difference between magnifying something 100x and then 430x, between which there are 330 increments as opposed to just 45.

Kenny

#6 Hikari

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Posted 28 May 2013 - 12:00 PM

Kenny, think of it this way. Making something twice as large is not really a significant jump, especially if you are looking for detail. Much of what you can see at 2x, can be seen at 1x. Jumping to 4x makes a good difference, especially if you are limited.

#7 KennyJ

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Posted 28 May 2013 - 12:20 PM

Yes I understand that,Hikari.

Is it just co-incidence then that most microscopic subjects, regardless of what they are, happen to benefit from those two particular magnifications, as opposed to say, 50x or 200x or 300x magnification?

Kenny

#8 Hikari

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Posted 28 May 2013 - 12:58 PM

Kenny, it has to do with specimen size. For a biological microscope, 10X and 40X objectives (100X and 400X) are very common to use. Structures seldom need more or less magnification. I would imagine 99% of the work that is done in our lab is between 10X and 40X.

For lower than 10X, a stereoscope is a better instrument. There are 4x and 5x objectives, but they are mostly used for searching. I have a 2x objective that is almost never used.

Above 40x for biological specimens becomes very difficult for the narrow depth of field. We can make image stacks automatically to overcome that, but the images are still hard to make. The limit to optical microscopy is 100X (1000x visually). After that, you can make images bigger, but you can no more detail.

There are a few ways to work at high magnification and get really nice images, but those are not visual techniques. Right now, we are looking at drafting a grant for a confocal microscope which uses a tiny disk to eliminate the out of focus light and only record the light at the sample plane. That actually works best at magnifications of 40X or higher. Actually, these microscopes don't use magnification as we would think of it--they make images by scanning the field and so to "change" "magnification" you just scan different field sizes. Leica make really nice confocal microscopes--for between $600,000 and $1,000,000 they can set you up with a really nice system. Going to a Japanese manufacturer does not save you much. The annual service contract can be about $30,000.

#9 ASTERON

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Posted 28 May 2013 - 02:28 PM

Hi Hikary,
$600,000 - Not Bad.:jawdrop: - I just happen to be short on small change right now :roflmao:

I actualy recently got myself a great deal on a used trinocular Zeiss Axiostar that needed some spare parts. When I contacted the local Zeiss agents, I got a nasty surprise. A Pair of new eyepices for the microscope cost here more than I paid for the entire Axiostar package (including a Pixelink CMOS video camera).
I will probably get me a pair of El Cheapo Amscope 10X widfields for $50.00 on eBay and live with them happily ever after.
BTW, is there any good excuse for the scandalous prices of Zeiss microscopes and parts taking into account that they are actually made in China or Mexico ?

#10 cpsTN

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Posted 28 May 2013 - 04:07 PM

The scope does not say a model that I can find, but does say "ST", which I assume means student. The turret has spots for only two objectives and those are 10x and 43x. The only EP I have is a 10x, which is why my OP was about 100x and 430x. I am going to get a 15x and perhaps a 20x EP, but definately the 15x. Should I get more EPs or more objectives? Are objectives standard sizes (physical) like the EPs are (23mm)?

#11 ASTERON

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Posted 29 May 2013 - 01:46 AM

Charles,
Getting a x15 is a bit close to your x10.
. X20 seems more logical to me unless you want something closer to the mag provide by the x10.
With regard to eyepieces, I will give priority to getting objectives as the eyepieces just magnify the image created by the objective.
And no, not all objectives have standard threads.
While there are a few standards around, some objectives may be different, so you better verify that what you buy will match your microscope.
Assuming its aN old microscope it would probably have a non- infinity type of objective. I assume you will want an air objective ( non oil).
Your best bet is buying a used B&L objective from the same series as your current objectives. If you can't find one, you must make sure that what you get has the right type of threads and is designed for the correct tube length of your particular microscope.
Sorry if this sounds confusing,
Just my 2 cents.
Maybe Hikary can help also.



#12 Hikari

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Posted 29 May 2013 - 02:35 PM

+1

I would start with the 20X EP. The 15X is not a great jump. With a 20x you will have 10x, 20x, 43x, and 86x. The only reason I might get the 15X is if you find the the 86X not very satisfying because the image quality. Most research microscopes have a spread of 5x, 10x, 20x, 40x, and 100x. The 20x EP would get you close to that.

#13 cpsTN

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Posted 29 May 2013 - 07:10 PM

Great. I will get the 20x. Here is a pix of a very similar scope. Mine is the same as this, but mine has only two objectives not three as does this one.

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