Phase Contrast w/out a Centering Telescope?

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hoarybat
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Phase Contrast w/out a Centering Telescope?

Post by hoarybat »

Hi all,

I'm becoming familiar with using phase contrast illumination on my new Zeiss Standard scope. I've found aligning the condenser annulus with the objective phase plates fairly straightforward at 10x, difficult at 40x, and very difficult at 100x. I feel like a centering telescope would be most helpful, but want to avoid purchasing unnecessary accessories.

Do you all rely on CTs for your phase contrast alignment, or is it possible to eyeball the alignment with good results and fine tune by observing the phase contrast effect in the image?

Thanks in advance,

Dan

Charles Krebs
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Post by Charles Krebs »

With some patience, centering telescopes can usually be found at very modest prices.

But if you do not have one, a useful "trick" is to pull one eyepiece out (or use a spare eyepiece) and carefully hold it up, top to top (eye-lens to eye-lens) to the other eyepiece that is still inserted. Look into the back of the eyepiece you are holding and you can get a very good look at the objective rear aperture.

I've been able to adjust a condenser with one hand (a bit awkwardly since there are two adjustments... you need to go back and forth). If you find that you really need two hands it is a very simple matter to come up with a way to quickly and temporarily hold the eyepiece in position.

Pau
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Post by Pau »

The telescope eyepiece is an useful accesory, not only for phase contrast. I didn't know the Charles trick but you can also do it just looking into the microscope tube without eyepiece, but when used to phase contrast you can aling it just looking the phase image while moving the centering knobs as you say.

You don't need an original Zeiss one, any other with the same diameter likely will be equally useful, I have a very old Zeiss Jena one and I find it more comfortable than the original Zeiss west.
Pau

hoarybat
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Post by hoarybat »

Thanks for the great information, as usual. I'm very grateful for the patience and expertise extended to impatient newbies like me.

A follow-up question:

Is the correct diameter 23mm or 23.2mm? I've seen both figures bandied about, and I can't tell what the correct one is. Unfortunately, my calipers are on-loan to a friend, or else I'd measure the eyepiece diameter myself!

Pau
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Post by Pau »

hoarybat wrote:Is the correct diameter 23mm or 23.2mm?
I think it's the same, I only know about two microscope eyepiece standards: 23.2 mm often just named "23" (from the RMS standard and still very usual in today low end microscopes) and 30mm, the most usual in widefield modern microscopes and most steremicroscopes. There are also some stereos with 30.5 eyepieces.
Pau

hkv
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Post by hkv »

Got my centering eyepiece/telescope for $30 on ebay in like new condition (Olympus U-CT30). Sometimes you can find them really cheap. Look for them on ebay for a month or two and you will find one for a reasonable price.

hoarybat
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Post by hoarybat »

The Zeiss Optical Systems for the Microscope brochure (41-101-a, November 1971?) states that their tubes have an inside diameter of 23.2mm. I'm willing to bet that referring to "23mm" is just shorthand.

I'll keep an eye out for a centering telescope on eBay -- most of the examples I've seen have been ~ $100, which seems unnecessarily high.

hoarybat
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Post by hoarybat »

Thanks to a greatly-appreciated tip from Pau, I acquired a reasonably priced centering telescope.

It's much easier to align phase rings with the telescope, and the phase effect is much more pronounced when it's quite properly aligned.

I'm very happy with how my equipment is working!

NicoVB
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Post by NicoVB »

Little question about that CT.

It's described in the manual:
Looking through the centering telescope, rotate the top lens assembly of the CT until the bright light (light annulus) and the dark ring (phase annulus are sharply focused.

Do they mean this?
Image

If yes, then there is something wrong with my CT, because it's stuck, i can not rotate the top from the buttom section
When you make the most fantastic discovery, a lot of people want a piece of it...

Pau
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Post by Pau »

Yes, it seems. You must be able to modify the distance from the top to the bottom section to focus it, other models do it just pulling/pushing. Likely the grease has harden, sometimes heating it with a hair dryer allows to free it

But if it's already focused this doesn't seem urgent, although it will be convenient if you want to inspect other optical planes.
Pau

NicoVB
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Post by NicoVB »

Alas, it's not focused.
I tried the objective on objective approach, but i suffer from double vision due to my lens implants, and i see 4 rings.
Hard to line up that way.

Time for some WD-40 penetrating oil.
When you make the most fantastic discovery, a lot of people want a piece of it...

Alan Wood
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Post by Alan Wood »

NO - Do NOT use WD-40.

The best stuff for this solidified Olympus grease is isopropyl alcohol.

Apply a few drops to the exposed threads and let it soak in. Repeat until the movement loosens. Mine took about an hour to get it unstuck.

Then clean out all of the old grease, again using isopropyl alcohol, and apply a suitable lubricant.

Alan Wood

NicoVB
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Post by NicoVB »

No luck... i guess i need to go brute force on it. ](*,)
When you make the most fantastic discovery, a lot of people want a piece of it...

NicoVB
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Post by NicoVB »

Oh yeah...
Brute force worked :D
When you make the most fantastic discovery, a lot of people want a piece of it...

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