Olympus CH-30 questions

ChrisR · Post by **ChrisR** » Sun Mar 24, 2013 7:22 pm

I want to look at some things with transmitted light, for about the first time

I have most of a CH-30, and an old CH2

The CH30 had no condenser - I have one from another Olympus which fits, (NA1.25 I assume they're compatible), but none of the red, blue, green parts.
For the field diaphragm I think I can use rings of black paper. I can make a filter holder should I need it but I don't know what the compensatiing lens is for . ? ?
Currently also missing a bulb so I haven't tried it.

At the position arrowed, right above the objective, the CH30 has a thick block of glass. The CH2 has a dust-gathering empty tube ( Chrome plated inside

).
I'm a bit surprised that such a thickness of glass doesn't introduce aberrations, in a finite scope?
Any point removing it?

Charles Krebs · Post by **Charles Krebs** » Sun Mar 24, 2013 11:29 pm

I believe the the "compensating lens" (blue circle) is Olympus part CH3-AL which attaches to the bottom of the condenser made for the CH-30 (CH3-CD). There is no built in condenser adjustment on the CH-30 (just up and down). With this attached to the condenser bottom you can center the field diaphragm that is obtained by using the "red circle" component (CH3-FS). If all is centered properly as the factory intended this should not be essential,and the CH3-AL may not fit on the condenser you have anyway. BTW... check out Ebay 271142683152, I think this is the same piece.

I can't speak directly to the CH-30, but I am not so sure the lack of a field diaphragm is that critical most of the time. If you have one it is certainly good technique to use it appropriately as you change objectives. I've have been surprised at the small number of occasions where it seems to provide a significant reduction in flare with my BHS. However this will likely vary from scope to scope.

The green part is a filter holder. Not essential at all really.

I'm not 100% sure about the the optic or "glass" at the top of the frame (yellow arrow). Since the CH-30 has a reversed nosepiece I suspect it is there to "optically maintain" the correct 160mm tube length required by the objectives. The CH-2 does not have a reversed nosepiece. I would not mess around with it. (You see something similar on the BHTU versus BHT microscopes. The fixed, reverse nosepiece stands, BHTU have "glass" there, the non-reversed nosepiece BHTs do not).

BTW... check out Ebay 271142683152

ChrisR · Post by **ChrisR** » Mon Mar 25, 2013 7:03 am

Great thanks Charles

ChrisR · Post by **ChrisR** » Sat Mar 30, 2013 4:22 am

I found the solid cylinder of glass, orange arrow, about an inch long, came out very easily (2 screws). It appears to be flat top and bottom, which surely would add aberrations?

I'll try the scope with tube/camera on top, with the lump both in and out.
--
Objectives which came with this, like the ones you get on a CH2, are 4x, 10x, 40x and 100x. So there's a bit of a gap where 20x is missing. It seems that Oly didn't make one.
Nikon CF aren't parfocal.
Can anyone suggest what would suit, pricewise (the whole scope cost less than a Nikon CF objective) and be parfocal?

I compared the Olympus objective with a Nikon CF 10x 0.30, and admit I was disappointed that through the eyepiece, I could barely see any difference at all. Subject-dependent, perhaps.
--

Next question, if I want to use my specs, would "any" Olympus/Nikon wide-field eyepiece work? (23mm, microscope, single). Or do I need "high eyepoint"?

Alan Wood · Post by **Alan Wood** » Sat Mar 30, 2013 4:54 pm

ChrisR wrote:Objectives which came with this, like the ones you get on a CH2, are 4x, 10x, 40x and 100x. So there's a bit of a gap where 20x is missing. ... Can anyone suggest what would suit and be parfocal?

Next question, if I want to use my specs, would "any" Olympus/Nikon wide-field eyepiece work? (23mm, microscope, single). Or do I need "high eyepoint"?

According to the brochure:
http://www.alanwood.net/photography/oly ... s.html#ch3

the CH30 was supplied with long-barrel (45mm parfocal) objectives, either the education EA range or the A range.

Any Olympus 20x of that vintage (A, D Plan, S Plan or S Plan Apo) should be parfocal.

The Olympus eyepieces with a high eyepoint for spectacle wearers include "H" in their designation, so the CWHK, NCWHK and WHK should all be suitable, but not the WK.

Alan Wood

ChrisR · Post by **ChrisR** » Sun Mar 31, 2013 3:54 am

Thanks
The objectives I have which all came together, appear to be for the older/earlier lower spec CHA/B/2, presumably the base series listed on page 4 of
http://www.alanwood.net/downloads/olymp ... ations.pdf
and therefore not long barrel.

There are some 20s in the list but weren't in the standard stand + objectives packages, it seems. I don't remember seeing any.

Does anyone know if those objectives are likely to be parfocal with other makes at the time, or anything about any eyepiece corrections the objectives would be designed for?

Alan Wood · Post by **Alan Wood** » Sun Mar 31, 2013 4:53 am

ChrisR wrote:The objectives I have which all came together, appear to be for the older/earlier lower spec CHA/B/2.

Does anyone know if those objectives are likely to be parfocal with other makes at the time, or anything about any eyepiece corrections the objectives would be designed for?

You can see those objectives and the matching eyepieces in the Olympus High Quality Optics brochure here:
http://www.alanwood.net/photography/oly ... ds.html#bh

The normal achromats just have a number to indicate magnification. The flat-field ones say "Plan" next to the magnification.

The only high-eyepoint eyepieces seem to be the WF ones; they were standard on the BH microscopes and are fairly easy to find.

Alan Wood

Charles Krebs · Post by **Charles Krebs** » Sun Mar 31, 2013 11:11 pm

Does anyone know if those objectives are likely to be parfocal with other makes at the time, or anything about any eyepiece corrections the objectives would be designed for?

As far as parfocal goes I don't think there was much of a "standard" between manufacturers for quite some time. Then there was a JIS standard (36mm parfocal) and a DIN (45mm parfocal). The DIN became the closest thing to a "universal" standard. Some still adhere to a 45mm parfocal distance, but with the infinity optics that has eroded a bit as well.

See second column on page 55 here:
http://www.klaus-henkel.de/mikrofibel.pdf

Eyepiece compensation is an even bigger can of worms. There was no standardization between manufacturers. About the best you can do is to try and track down old brochures and instructions and try to use the recommended eyepieces. Most of the time (but I do not believe always) corrective or "compensating" eyepieces were marked with either a "C or "K" (as in WHK-10X).

ChrisR · Post by **ChrisR** » Mon Apr 01, 2013 2:06 am

Thanks.
Charlie - A nice document. Translating my way through the whole, thing will expand my German vocab somewhat!