ANyone know much about microscopes?

[blindswelledrat]

Hello
At the weekend I found my old microscope that my mother bought second hand for me from a laboratory when I was a kid.
I've dusted it off and my kids are loving it, but it's quite a complex thing and there are several things I can't work out and need help using/maintaining it.:

1) How do you clean the lenses? Its has 4 different lenses which rotate, but the end of them is almost a pin-prick so you can't actually wipe them at all.

2) It has a brown, unlabelled, bottle of fluid of some kind. What is that for?

3) It has many back-lighting options. Is there an optimum standard or do you use them all?

4)Given that it is back-lit, is it possible to view solid objects like insects, for example, or will it only view thin sections that let the light through?

5) I cannot get any kind of focus with the two highest magnification lenses. Any tops on what I might be doing wrong?

Thanks

[Simpo Two]

1) As long as the surface of the glass is reachable try a lens cloth or tissue with meths on it.

2) Might be Canada balsam, used to fix small objects onto slides.

3-4) You'd use backlighting (a small light and/or mirror underneath the platform) for translucent objects, and top lighting for solid objects. If it doesn't have that built in, try a table lamp or sunny window - the problem may be getting the light into the small gap between lens and subject.

5) The higher the magnification the closer you need to get. Have you tried winding down the lens until it's right on the object, then slowly turning back? It should snap into focus somewhere.

[spikeyhead]

It's possible that the liquid is immersion oil. Can you post up exactly what is written on each of the four objective lenses?

To focus the microscope, start of with the minimum magnification lens selected. Carefully adjust the focus to be as clear as possible. Rotate to the next magnification and refocus. This should only require a very minor change. Once that is as good as you can get, then select the next magnification and repeat. Get it a bit wrong and you can crash the higher mag lens into the slide.


A little light reading on oil immersion.
http://en.wikipedia.org/wiki/Oil_immersion

[blindswelledrat]

spikeyhead said:

It's possible that the liquid is immersion oil. Can you post up exactly what is written on each of the four objective lenses?

To focus the microscope, start of with the minimum magnification lens selected. Carefully adjust the focus to be as clear as possible. Rotate to the next magnification and refocus. This should only require a very minor change. Once that is as good as you can get, then select the next magnification and repeat. Get it a bit wrong and you can crash the higher mag lens into the slide.

spikey, this is more or less what I did. (i'll post what was written on each lense later). It worked for the first two.
It seemed to me that the longer lenses were almost too long to do this. Is it possible that the binocular eyepiece inserts are too high a magnification or something? (they say 15 X on them?) or is this comepletely irrelevant?

[blindswelledrat]

Simpo Two said:

1) As long as the surface of the glass is reachable try a lens cloth or tissue with meths on it.

2) Might be Canada balsam, used to fix small objects onto slides.

3-4) You'd use backlighting (a small light and/or mirror underneath the platform) for translucent objects, and top lighting for solid objects. If it doesn't have that built in, try a table lamp or sunny window - the problem may be getting the light into the small gap between lens and subject.

5) The higher the magnification the closer you need to get. Have you tried winding down the lens until it's right on the object, then slowly turning back? It should snap into focus somewhere.

CHeers. With regards to 3 - 4 I wondered about the top lighting. Given the complexity of the microscope I am surprised it doesn't have something in-built. Or maybe it has and I haven't discovered it yet.
With regards to the Canada balsalm: I thought it might be something like that, or oil for the moving parts of the microscope. How will I tell?

[spikeyhead]

blindswelledrat said:

spikeyhead said:

It's possible that the liquid is immersion oil. Can you post up exactly what is written on each of the four objective lenses?

To focus the microscope, start of with the minimum magnification lens selected. Carefully adjust the focus to be as clear as possible. Rotate to the next magnification and refocus. This should only require a very minor change. Once that is as good as you can get, then select the next magnification and repeat. Get it a bit wrong and you can crash the higher mag lens into the slide.

spikey, this is more or less what I did. (i'll post what was written on each lense later). It worked for the first two.
It seemed to me that the longer lenses were almost too long to do this. Is it possible that the binocular eyepiece inserts are too high a magnification or something? (they say 15 X on them?) or is this comepletely irrelevant?

The X15 on the eyepieces is irrelevant to the working distance between the objective and the work. There's a table close to the top of this link that shows just how small the working distance is for high mag objectives.

http://www.microscopyu.com/articles/formulas/formu...

It's likely that there will be less than 0.3mm for a X40 objective, hence it's critical that the focus is well adjusted on the lower magnifications first. It's also possible that the high mag lenses have been damaged.

[Simpo Two]

blindswelledrat said:

With regards to the Canada balsalm: I thought it might be something like that, or oil for the moving parts of the microscope. How will I tell?

Good question, not sure! I guess balsam will be sticky and oil wil be oily

IIRC focus oil is used to 'connect' the lens with the slide for refractive reasons I can't define now.

Re spikeyhead's point abut not cracking the slide when trying to focus, that's why it's better to start close and go up, not the other way.

[blindswelledrat]

spikeyhead said:

The X15 on the eyepieces is irrelevant to the working distance between the objective and the work. There's a table close to the top of this link that shows just how small the working distance is for high mag objectives.

http://www.microscopyu.com/articles/formulas/formu...

It's likely that there will be less than 0.3mm for a X40 objective, hence it's critical that the focus is well adjusted on the lower magnifications first. It's also possible that the high mag lenses have been damaged.

Actually X40 is the lowest magification of the 4 lenses, and the focal point is indeed a short distance (although I would guess at about 20mm) (well I say lowest - it is definitely the shortest of them and the next shortest is definitely a higher magnification). I don't think the others have the magnification written on them in the same format.
It certainly helps to know that the focal distance will be lower still for the bigger lenses. I can try along those lines and determine whether they are, indeed, damaged.

Edited by blindswelledrat on Tuesday 27th January 15:45

[Simpo Two]

If my schoolboy microscope is anything to go by (it's still upstairs in a box) the highest magnification lenses are effectively unusable due to lack of light, and the working distance is only a few mm. Lower the lens until it's 0.5mm from the object, then very slowly go up. The plane of focus will flash past.

[blindswelledrat]

Simpo Two said:

If my schoolboy microscope is anything to go by (it's still upstairs in a box) the highest magnification lenses are effectively unusable due to lack of light, and the working distance is only a few mm. Lower the lens until it's 0.5mm from the object, then very slowly go up. The plane of focus will flash past.

Ill try this. I left it at my mothers so I cant do it until next week.
THe lack of light shouldn't be a problem as it has so many different light settings and I think it is a cut above the average schoolboy microscope

[Simpo Two]

As undergraduates we used Leitz binocular microscopes rather like the one below - very nice: