Setting up a Zeiss Standard RA

75RR · Post by **75RR** » Sat Jan 31, 2015 12:35 pm

Thought I would start a new thread as the other one ( http://www.photomacrography.net/forum/v ... hp?t=25202 ) was getting rather long and covered several areas.
Finally got the Zeiss Standard RA up and almost running.
I say almost because it is a big step up from my Zeiss Standard Junior and I could do with the setting up procedure so every thing is as it should be.

Is there an order and technique one should follow in centering everything?
Not sure of the function of the lens below the condenser.
Lighting is with the original 12v 60w bulb at the moment. Led to follow soon.
Have parfocality on the photo tube, albeit at the very top of its range.

Pau · Post by **Pau** » Sat Jan 31, 2015 1:17 pm

Good looking scope, congrats!

In these models almost all is centerable...so it's also decenterable

. Be patient with centering, don't touch what is working well: it's easy to go wrongly, I have experience!

Aside of the obvious, the condenser, you can also center
- the auxiliary sub condenser lens: it has two or three small screws
- the dovetail mounts with the bolts at female dovetail holders (removing the screws that hide and lock the actual bolts that hold the dovetail in place).
- the mirror/field diaphragm assembly also can be regulated a bit losing the fixation screws and playing about 1 mm with its position
- even the arm to base fixation playing with by the same system

The auxiliary lens is in principle intended to get more even illumination with low power objectives. With your 0.9NA condenser it isn't that necessary but can improve illumination in some cases. I use it most the time with my DIC hybrid setup because it allows to put the condenser at different height.

I have not a good method to center the microscope, so I'm interested to know if there is one too.

The simplest and more important centering operation is with the condenser. Often you need to center it for each objective but the usual approach is to begin with low power focusing the field diaphram with the condenser at the slide plane (standard method for Köhler) and improve it for each magnification step. If when you go downwards it remains approximately centered, your scope is likely to be well centered.
If when putting the subcondenser lens the field diaphram image decenters, try to center that lens

75RR · Post by **75RR** » Sat Jan 31, 2015 2:31 pm

Good looking scope, congrats!

Thanks. I smile every time I uncover it!

In these models almost all is centerable...so it's also decenterable

So I gathered. I am taking deep breaths!

The simplest and more important centering operation is with the condenser. Often you need to center it for each objective but the usual approach is to begin with low power focusing the field diaphram with the condenser at the slide plane (standard method for Köhler) and improve it for each magnification step. If when you go downwards it remains approximately centered, your scope is likely to be well centered.

Sounds like a plan.
Also have to learn to set up Köhler :)

Many Thanks

75RR · Post by **75RR** » Sun Feb 01, 2015 5:36 pm

Had forgotten that I had to focus and center the 12v 60w illuminator as well!

Think I finally got a hand on Köhler. Unless I got it wrong, it is much less complicated than everything I have read implies.

Still have quite a bit of variation between objectives - in terms of where each one is and the actual center - given that most of the articles I have read mention centering the objective as part of the köhler set up, I take it that some variation from the actual center is to be expected?

Pau · Post by **Pau** » Mon Feb 02, 2015 4:04 am

75RR wrote:Still have quite a bit of variation between objectives - in terms of where each one is and the actual center - given that most of the articles I have read mention centering the objective as part of the köhler set up, I take it that some variation from the actual center is to be expected?

Some center variation is to be expected with microscopes of that age, I also experience it, in fact it isn't that important (petrographic scopes where centering is more critical often have centering systems at the objective itself or at the nosepiece)
These objectives are approximately parfocal and parcentric, so no exactly.
A bit decentering doesn't affect the image except with some critical applications like darkfield at the NA limit, phase (you always need to center the condenser annulus) or DIC (again it's agood idea to regulate the prism position for each picture)