Through the microscope

Posts tagged ‘LOMO’

Centring a lomo or meopta condenser

Scenario: You’re  trying to set up Kohler illumination on an old Lomo biolam or  Meopta microscope which has no centring mechanism on the condenser. You have the lamp centred and the field diaphragm pretty well centred and you’re ready to get the condenser centred. You pop your phase telescope in the eye tube, you look through it and horror of horrors you see something like this!

iris aperture squiffy

 

Your iris aperture (condenser aperture) is way off centre. When you enlarge the aperture part of it disappears out of view. Kohler is impossible. You’ve wiggled everything that can be wiggled and you’re about to start smacking things with a hammer in frustration. STOP! There is a solution and no microscopes have to be hit with anything.

Step 1) Remove the condenser and the stage – this shouldn’t be a problem, they come off fairly easily, especially if you remove the mirror so you can get a screw driver in more easily.

 

Removing Lomo stage

Removing Lomo stage

Step 2) Observe the condenser carrier. You will see a knurled locking screw and three tiny grub screws  – one at the front and two at the back on either side. These tiny grub screws are your centring mechanism but don’t bother trying to alter them yet, nothing will happen until you have taken off the locking ring.

Locking ring

Locking ring

 

Step 3)  Unscrew the locking ring -I used pointy ended pliers to get it started. Now you can  adjust the grub screws. Pop the condenser back while you do the adjustment. Rack the condenser almost completely up and look through the phase telescope using a low power objective. Make sure the objective is down near where the stage should be. It’s no good leaving it 20 cms up in the air.  It doesn’t matter that you have no stage and no slide to view, you’re only looking at the condenser aperture through a phase telescope.

Approximate position of grub screws shown by pink arrows

Locking ring removed. Approximate position of grub screws shown by pink arrows.

 

Step 4)  Adjust the grub screws until you see something resembling this through the phase telescope.

iris aperture central

 

Step 5)  Cry “Hallelujah!” then throw the locking ring in the bin. Well, put it somewhere safe, I have found everything to be perfectly secure without it and it’s much easier to adjust without it there.

Step 6) Put the stage back on. Good luck with that, it’s fiddly. Put the mirror back on, put on anything else you removed.

Now you can set up Kohler in the usual way.

NB. you may have to adjust the head  if that is out of whack rather than the condenser. The head has a dove tail slider which is obvious and easy to adjust. You have probably wiggled it several times during your attempts to get the condenser centred.

 

 

 

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Gallery

My first diatoms

I have been brave today, I tried lots of new things I haven’t tried before. I used immersion oil for the first time, I used my Lomo aplanatic oblique condenser (oiled) and I tried taking the photos with eyepiece projection – I have never tried that before either. I have been so organised that I have managed to do a compare and contrast of relay lens versus eyepiece projection, I think I prefer eyepiece projection.

I have also mowed the lawn and planted violas in the front garden.  Very lovely they are too, the post lady will be pleased.

Oiling a condenser is messy, finding diatoms under oil immersion is a pain in the posterior but I think I did okay for a first attempt. Something needs cleaning but I’m not sure what. There are blobules in the same place in every shot. I can only assume it’s on the bottom of the condenser. I’m still chuffed though.

All pictures were taken using the Lomo microscope with 1.4 na aplanatic oblique condenser, and 90x oil immersion objective (na 1.25). Some 50 year old cedarwood immersion oil that i fpound in an old condenser box was used for oiling both the condenser and the objective.  The only difference was the photography; a Canon EOS 1100D was used to take all the pictures, but the pictures marked “relay lens” used the Brunel universal camera adapter (2x) and  the pictures marked “eyepiece projection” were taken using a Zeiss projective 8X eyepiece.

Click on the pictures to make them larger…

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