A Dabble with makeshift darkfield and oblique

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mrsonchus
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A Dabble with makeshift darkfield and oblique

#1 Post by mrsonchus » Tue Nov 27, 2018 11:50 pm

Hi all, I've been collecting mosses today and thought rather than just have a quick look with the stereozoom 'scope, I'd have a look with the mighty Orthoplan and attempt a very crude darkfield, my first try with the Orthoplan.

I cut a small very rough 'circle' of black card about 6mm diameter and placed it in the middle of the top of the bottom lens (that is the low 0.25 N.A. lens) of the 1.25 N.A. 603 condenser fitted. The swing-in/out nature of the Leitz 600 series condensers makes it really easy to place a darkfield mask effectively inside or inbetween the low N.A. bottom lens and the high N.A. top lens, very convenient.

Then I swung in the top lens as usual for objectives above N.A. 0.25 with this condenser (which for my objectives means 10x and upwards inclusive, as the 10x has an N.A. of 0.3) and had a look, The effect whilst very good, with a lovely dark field (although this very rough & ready mount in 50% PVA and 50% glycerin was full of tiny reflective motes of dust - the worst curse for darkfield but anyway....) - is you may say 'a little ropey at this stage'.

The specimen - a sprig of moss with several branches - certainly not flat but really pretty thin, with a coverglass added, lit-up quite well for such a very crude setup.

The principle definitely works and I will surely pursue this with 'proper' mounts and 'proper' masks - truly round and centered for starters!

Rather crude and pretty awful, but a start.....

Here's the very basic darkfield image, by no means technically good, but very encouraging considering how crude my setup was....
ws_stack1.jpg
ws_stack1.jpg (51.46 KiB) Viewed 1050 times
Whilst basically messing about with the darkfield-stop to-be, I tried using the centering screws to move the condenser off-center to varying extents and in various directions. Again, crude but promising oblique images showing a great deal of extra information in a 3D sort of way. The details of the cell walls and chloroplasts etc are really considerably enhanced I found, very handy for such low-contrast and translucent material as unstained live moss....
ws_stack2.jpg
ws_stack2.jpg (57.2 KiB) Viewed 1050 times
and,
ws_stack3.jpg
ws_stack3.jpg (49.62 KiB) Viewed 1050 times
ws_stack4.jpg
ws_stack4.jpg (63.32 KiB) Viewed 1050 times
ws_stack5.jpg
ws_stack5.jpg (51.35 KiB) Viewed 1050 times
Sorry to be brief - I'll post images of how I did these tomorrow, and maybe a few more of the mosses....

John B.
John B

MichaelG.
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Re: A Dabble with makeshift darkfield and oblique

#2 Post by MichaelG. » Wed Nov 28, 2018 12:11 am

That's a great demonstration of the possibilities, John

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Hobbyst46
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Re: A Dabble with makeshift darkfield and oblique

#3 Post by Hobbyst46 » Wed Nov 28, 2018 7:40 pm

I like the view of the "leaf" cells in these photos, especially the two bottom photos, which show whole undamaged cells in all their beauty and detail. They make me eager to try similar moss preparations and observations; the bryums (?) in my garden have grown to 6-7 mm in height. Regretfully, I lost the chance of winning the AO-570 stereoscope which I had tried and liked; instead, there is a chance of winning an Olympus VMZ stereoscope.

Dear Olympus experts, does anyone know whether the external diameter of the eyepieces of an Olympus VMZ is 23.2 or 30-30.5mm? I could not locate this spec in the brochure, neither in the instruction manual (from the alanwood.com site).
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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Crater Eddie
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Re: A Dabble with makeshift darkfield and oblique

#4 Post by Crater Eddie » Wed Nov 28, 2018 8:20 pm

Very good results for the first go there John. I hope to see more of these soon.
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75RR
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Re: A Dabble with makeshift darkfield and oblique

#5 Post by 75RR » Wed Nov 28, 2018 9:04 pm

Really like images 2 and 3 :) Nice!

Dear Olympus experts, does anyone know whether the external diameter of the eyepieces of an Olympus VMZ is 23.2 or 30-30.5mm?
More of a detective than an expert.

This is from the Olympus VM Stereoscopic Microscope brochure, page 10.

Diameter of eyepiece micrometer on the GW10x eyepiece is 24mm
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Re: A Dabble with makeshift darkfield and oblique

#6 Post by Hobbyst46 » Wed Nov 28, 2018 9:15 pm

75RR wrote:Really like images 2 and 3 :) Nice!

Dear Olympus experts, does anyone know whether the external diameter of the eyepieces of an Olympus VMZ is 23.2 or 30-30.5mm?
More of a detective than an expert.

This is from the Olympus VM Stereoscopic Microscope brochure, page 10.

Diameter of eyepiece micrometer on the GW10x eyepiece is 24mm
Great detective work! Dr. Watson: so the outer diameter can in no way be smaller than 24mm! so it is 30mm! Elementary!
Thanks, 75RR!
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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