Zeiss rotating stage

Andy Davies · Post by **Andy Davies** » Mon Oct 23, 2017 7:05 am

I have a Zeiss rotating stage that that has two knobs underneath which I guess must be for centering the stage but they do not appear to have any effect. I do not think they are for locking the rotation as a lever does this.

Andy ideas on what they do and how this stage could be centered?

Many thanks

Andy

Pau · Post by **Pau** » Mon Oct 23, 2017 9:16 am

IMO they must be for centering he stage as you guessed. If they don't work very likely it could be due to frozen grease, a common issue with items from its age. You can try moving the stage by hand while you turn each knob, but if I'm right you would need to dismount, clean and re-lube them
The more common XY rotating stage has two square head bolts to center it but I can't see it in yours that seems a more precision model.

Cactusdave · Post by **Cactusdave** » Mon Oct 23, 2017 1:13 pm

Pau is probably right that those must be centring knobs. It looks to me that the original stage has been customised. The four small cross headed screws in the bottom part of the stage in the first picture aren't Zeiss originals and it looks like the circumferential cord and spindle mount have been added at some point to motorise and control stage rotation.

Eddie · Post by **Eddie** » Mon Oct 23, 2017 1:50 pm

The two knobs under the stage are not for centering the stage. On Zeiss rotating stages there are no means to center the stage. Only the POL objectives are center-able. I believe one knob controls the click action of the stage from smooth, no-click rotation to clicks at certain degrees of stage turn. The other I believe turns the stage. Usually the one that turns the stage does not work properly.

Andy Davies · Post by **Andy Davies** » Mon Oct 23, 2017 4:12 pm

Yes, I've just found out from Spike Walker that Eddie is right!

I added the modification for motorising the stage which works great but it is a real pity that it can't be centred

Pau · Post by **Pau** » Tue Oct 24, 2017 1:17 am

Good to know! All petrographic microscopes I've used have center-able stages and I was sure that the center-able objectives were just to make them perfectly parcentric.
I've been tempted to buy one of such stages for my microscope hoping better centering mechanism than my center-able Zeiss rotating X-Y stages, now I'm not. I don't have any center-able objective and only one single objective center-able nosepiece.
Andy, could you link to the Sipike Walker source?

Eddie · Post by **Eddie** » Tue Oct 24, 2017 4:37 am

If you think about it, centering the stage to an objective is more troublesome if you are using more than one objective. Each time you change objectives, you would need to center the stage, which means going back to a previously objective used, would still need to be centered again. Whereas using centerable objectives, you can center each objective and switching objectives doesn't require you to recenter them. Same for individual single objective holders where each holder can be centered for that objective and centerable objective turrets where each objective can be centered in the turret.

Eddie · Post by **Eddie** » Tue Oct 24, 2017 4:55 am

That Zeiss rotating stage with the click enabled stage rotation along with the click enabled mechanical slide holder, is Zeiss' high end petrological stage. Not only does the stage click at certain degree intervals turned but the mechanical slide holder also clicks at certain degrees of the x-y axis movement which allows the petrologist to keep his eyes on the specimen through the eyepiece while manipulating the slide during point counting.

Pau · Post by **Pau** » Tue Oct 24, 2017 5:08 am

Yes I understand the design. Thanks for the info.
The drawback is that it will not be fully useful outside its intended application (a well factory centered stand and centerable objectives). For example for DIC and oblique the specimen orientation does matter and also just for photography framing it is convenient. Anyway I have other rotatable stages that do this role although its rotation lacks some precision.

Andy Davies · Post by **Andy Davies** » Wed Oct 25, 2017 3:33 am

I'm a friend of Spike's so he confirmed this by an email. A work around is a RMS centering adapter that screws into the nosepiece.

Does anyone know of a X4 Pol Z objective for sale?