Kohler Trouble

[MichaelG.]

.. what mneium really must do *first* is sort that stage out, ie. get it level.

Surely, not only will that be the reason of the plane of focus issues, but also probably why the lighting *seems* misaligned.

I am assuming that the stage fits with some sort of dove-tail.

I don’t know how true-to-life the diagram at III in the previously-linked manual is ... but, as drawn, the stage support looks rather delicate.

MichaelG.

[mneium]

Don't own an Olympus BH2, but as a 12v 100 watt Halogen puts out a lot of light (particularly as in order to maintain/extend bulb life it should be kept within a 9-11 volt range),

it would make sense that it should have an ND filter for most observations and that it be removed for say high magnification DIC and Darkfield.

Perhaps an actual BH2 owner, and there are several on the forum, can confirm. I am sure mneium will sleep better for it.

It seems to me that much of this is conjecture in terms of contributing in a major way to the lack of a decent image, and that what mneium really must do *first* is sort that stage out, ie. get it level.

Surely, not only will that be the reason of the plane of focus issues, but also probably why the lighting *seems* misaligned.

I am assuming that the stage fits with some sort of dove-tail.

>I am assuming that the stage fits with some sort of dove-tail.
It does, it's held in by one screw. https://i.imgur.com/sb4jELp.jpg

I am not yet sure what exactly is causing the unlevel stage because I don't have another BH-2 to see how it "should" fit. I suspect the screw *should* fit lower into the dovetail, not on the top like it is. The screw also does not seem long enough... I have to shove a piece of cloth between the screw and the dovetail to prevent the stage from wobbling. Yet it cannot be a non-original screw, because it can't be removed (it's captive.)
Perhaps the entire stage was bent during shipping.

As for the filters, it seems that the BHS originally came with an ND2 filter (which removes 50% of light) so I'll try one of those.

[75RR]

I am not yet sure what exactly is causing the unlevel stage because I don't have another BH-2 to see how it "should" fit. I suspect the screw *should* fit lower into the dovetail, not on the top like it is.

From what I have seen there is a groove that runs around the top of the stage holder. The stage seems to be in position at the back, the problem is at the front where the screw needs to be 'unscrewed' so that the front of the stage can drop down. It then needs to be tightened.

See photos of stage holder and stage. (Yellow circles highlight parts that fit into stage holder groove.)

[photomicro]

It does, it's held in by one screw. https://i.imgur.com/sb4jELp.jpg

I am not yet sure what exactly is causing the unlevel stage because I don't have another BH-2 to see how it "should" fit. I suspect the screw *should* fit lower into the dovetail, not on the top like it is. The screw also does not seem long enough... I have to shove a piece of cloth between the screw and the dovetail to prevent the stage from wobbling. Yet it cannot be a non-original screw, because it can't be removed (it's captive.)
Perhaps the entire stage was bent during shipping.

As for the filters, it seems that the BHS originally came with an ND2 filter (which removes 50% of light) so I'll try one of those.

This picture is *not* for your microscope, but one with a very similar stage I think. You should see that the screw really just pushes the dovetail of the stage itself, against the dovetail ring underneath.

My guess, is that at present, the whole thing is not seated right. Whether this is something that happened in transit is difficult to say, but really it should have been disassembled for long distance transport in a box or whatever.

Hopefully you can see from the diagram that undoing the screw should allow you to free the stage, and then 're-seat' properly. I do honestly think it is the root of your issues.

fig 1.jpg (23.46 KiB) Viewed 3547 times

As for the ND filter, I cannot see it is going to help any at all.

[mneium]

The stage does fit securely in the dovetail - it is clearly the way it's meant to fit. It just isn't level. I think the stage holder itself is warped/bent. Maybe will pick up another one.


Anyway, I'll try that and some filters and report back on results when they're here

[carlh6902]

The BHS has a tremendous amount of light. Your options for not obliterating your retinas are:

1) Turn the intensity down. It will likely be way below the "recommended" setting. That setting is (I believe) only appropriate with a neutral density filter in the system.

2) Add a neutral density filter in the lighting path.

Option 2 will provide a more appropriate light balance. This was critical in the days of film imaging. With modern digital cameras allowing for a custom white balance, option 1 is simpler.

Carl

[mneium]

For posterity, I did get the stage level. I employed some good old percussive maintenance. AKA: removing the stage holder, covering it with a towel, standing on the back & hitting it on the front lip with a hammer like a thousand times. Holy cow, they used thick gauge steel for this thing. I have no idea how it got bent upwards like that in the first place. It doesn't even seem easy to do intentionally. Anyway I can image the field iris properly now without any shims, and the lighting & focus is even across the plane.

When I get some ND filters - they're on the way - I'll report on whether or not they fix the blurriness/stray light I experience with the condenser open. Appreciate the advice, all - I would not have known that filters are a necessity for the BHS

This is a side-question I'd rather not create a thread for: does anyone know what the dedicated DIC/Phase condenser for the BH2 is called? The 1.4NA one with non-removable prisms. I've scoured all the manuals and threads but never seen a model name for it, only seen it called "the Nomarski condenser" in the BH2-NIC manual. They also seem extraordinarily rare. I read one source which said that the BH2-UCD Universal Condenser (which has an NA of 0.9) is just as good for DIC because the Nomarski prisms effectively lower the NA of the condenser to sub-0.90NA anyway. Is that true?

[75RR]

Anyway I can image the field iris properly now without any shims, and the lighting & focus is even across the plane.

I suppose all well that ends well ... QC miss at the factory?

[MichaelG.]

[…] Holy cow, they used thick gauge steel for this thing. I have no idea how it got bent upwards like that in the first place. It doesn't even seem easy to do intentionally. […]

Steel ... I’m astonished

From the photos, it looked like an alloy die-casting
... I had assumed it to be rather a delicate little thing.

Good outcome

MichaelG.

[Hobbyst46]

Steel ... I’m astonished
From the photos, it looked like an alloy die-casting
... I had assumed it to be rather a delicate little thing.
MichaelG.

They were steel in Olympus microscopes even prior to the BH2.

My applause to 75RR for pointing out to the non-level stage carrier.

[MichaelG.]

Thanks for the enlightenment, Doron

I was evidently mistaken in thinking that I recognised the little circles in the ‘stage holder.jpg’ posted by 75RR

MichaelG.