Second attempt at oblique dark field illumination of algae from neighbour’s pond using halogen swan-neck illuminator on Zeiss Standard microscope

This time I used my centrifuge to concentrate the sample – snow outside/cold means number algae per ml in the water low.

Bright field images of algae x40 objective – unfortunately they show that I have some work to do aligning the optics as lot of colour fringes…there is also quite a lot of dust on the optics of this microscope – I need to give it a good clean! However, not all out of focus rings are dust – much of it is algae in different planes on this live sample.

I particularly like the second and third pictures as they show long cilia from the spherical organism.

Video from this session showing motile organisms:

Dark field using oblique illumination – set up with Zeiss Standard microscope:

I have found that the best dark field is when the fibre-optic tips are placed on the stage pointing virtually horizontally at the end of the objective.

Dark field with x10 objective, using above equipment – looks like a star field in the telescope! Can you recognise the constellations?

The above two images came directly from the camera.

The following are the same two pictures but this time I have used curves in GIMP to remove part of curve below the data and hence blacken the background:

Dark field using x40 objective – this is where I am breaking new ground with success at dark field using x40 objective. So far, using my Zeiss IM microscope, I have been able to obtain excellent dark field images using the 10x non-phase objective and a phase annulus, but the higher power objectives don’t seem to work so well using that system. I think maybe the NA on the objectives is too high compared to the NA on the condenser, but am not sure of the reason.

I found that if I varied the position of the swan neck heads to direct the light more downwards (angled the lights to point down rather than horizontally) then this varied the lighting effect. The lighting is no longer true dark field but is still interesting! Example picture below:




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