Tiny field microscope specifically for diatom sampling

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MicroBob
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Tiny field microscope specifically for diatom sampling

#1 Post by MicroBob » Fri Apr 03, 2020 7:21 pm

Hi thogether,
photomicro-Mike had posted a link to a booklet of the Amateur Diatomist series: http://www.microscopy-uk.org.uk/diatomist/ADvol43.pdf

Beginning with page 4 an interesting design of a field microscope is shown that has proven well in practical use. The design specialty is that there is a cover slip fixed in focus and the sample is applied from the bootom and pressed to the cover slip. This is not useful for a general use microscope but it will be just fine for diatom collecting. I have collected and carried quite a few samples hill up and hill down only to see at home in the tent or holiday appartment that there are no diatoms but whatever other algae and mixed stuff. So a simple and compact means to quickly check a couple of spots for diatoms would be handy.
In this design a 1/2 inch objective is used. This equals a magnification of 12,5:1 on 160mm tube lenght. The actual tube length here is a bit shorter so this will be about a 10:1 magnicifation x eyepiece 10x = 100x.
The design is not complicated but it involves quite a bit of lathe work and it will take some time to machine this from available materials. But with a bit of thinking, cheap ebay stuff available and 3D printing it might be possible to develop something that can be built quickly.

Is someone else interested in this topic?

Bob
Last edited by MicroBob on Mon Apr 06, 2020 1:42 am, edited 1 time in total.

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daruosha
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Re: Tiny field mcroscope specifically for diatom sampling

#2 Post by daruosha » Fri Apr 03, 2020 10:03 pm

I'm thinking about a similar project and cobbled a 10X el cheapo objective with an LED and an eyepiece. It turned out the mechanical fit and finish is important and my 3D prints modeling (at least in my case) is not precise enough, everything needs to be on a very same axis and same horizontal level.

I need to read the PDF a few more times to digest it perfectly. However:

I love to buy one of these portable scopes:
Image

http://www.brunelmicroscopes.co.uk/handheld.html

They even have a model with pseudo phase contrast illumination. The OEM is Novel Co.
Last edited by daruosha on Fri Apr 03, 2020 10:25 pm, edited 1 time in total.
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Scarodactyl
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Re: Tiny field mcroscope specifically for diatom sampling

#3 Post by Scarodactyl » Fri Apr 03, 2020 10:10 pm

I suspect one of these little industrial or fiber optic examination scopes could possibly form a reasonable basis for a system. They are sometimes quite cheap anyway, I got two mostly complete examples for 20 bucks once.
https://www.ebay.com/itm/202781256892
At least this sort of scope gives you the eyepiece and objective mount in a reasonably compact package.
Last edited by Scarodactyl on Fri Apr 03, 2020 10:32 pm, edited 1 time in total.

MichaelG.
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Re: Tiny field mcroscope specifically for diatom sampling

#4 Post by MichaelG. » Fri Apr 03, 2020 10:26 pm

The Russian MIR-2 measuring microscope would probably make a good starting point for a Meakin style instrument.
See picture near the bottom of this page:
http://www.microscopy-uk.org.uk/mag/ind ... -Lomo.html

MichaelG.
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wstenberg
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Re: Tiny field mcroscope specifically for diatom sampling

#5 Post by wstenberg » Sat Apr 04, 2020 1:49 am

OK, I want to build one!
William
Dallas, Texas

Zeiss Standard WL with POL
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MichaelG.
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Re: Tiny field mcroscope specifically for diatom sampling

#6 Post by MichaelG. » Sat Apr 04, 2020 8:47 am

Here, for convenient reference is the important page 9
.
Meakin Field Microscope
Meakin Field Microscope
FF281EED-0E4C-4DCD-93A9-5D5E022FCFBA.jpeg (195.19 KiB) Viewed 558 times
.

MichaelG.
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MicroBob
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Re: Tiny field mcroscope specifically for diatom sampling

#7 Post by MicroBob » Sat Apr 04, 2020 9:25 am

Hi together, thank you for your comments!

The Swift FM31 and its clones are small but heavy and unwieldy to use. But they offer 400x magnification and can replace a normal microscope on a holiday trip to some extent. For this specific purpose I wouldn't use it. The fibre optics microscopes could be interesting and might already offer the right magnification. The Lomo MPB or MIR 2 is thin and short (20cm) but magnifies only 24x.
What I have is a Lomara field microscope from the 1920 or 30s that is light and thin and offers quite some magnification. Due to the thin tube diameter the image field is smaller though than possible with the design in the Amateur Diatomist. Since many people have spare objectives and eyepieces flying around it would be ideal to come up with a flexible design that can be adapted to the use with the available components.
While home 3D printing can do some things very well it is weak when it comes to sliding fits and threads. A seat to push in an eyepiece is no problem and the objective could simply be glued in or screwed into a glued in ring:
https://www.ebay.de/itm/Adapter-RMS-Thr ... 3780968401
or
https://www.ebay.de/itm/Parfocal-Length ... 2860034249

The focussing could take place over a solid state joint as the focus throw is small.

For the optical components a wide field eyepiece would be nice as it increases the area that is visible. Without a means to move the sample this becomes more important.
One might even use a 20:1 objective like the old Zeiss Jena or Lomo 33mm ones.

The whole thing should be small, light and robust to be carried in the jacket without being uncomfortable.

Bob

MichaelG.
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Re: Tiny field mcroscope specifically for diatom sampling

#8 Post by MichaelG. » Sat Apr 04, 2020 12:35 pm

MicroBob wrote:
Sat Apr 04, 2020 9:25 am
The Lomo MPB or MIR 2 is thin and short (20cm) but magnifies only 24x.
Sorry, Bob ... I was assuming that the objective and eyepiece of the MIR-2 would be replaced with something more suitable [they are standard RMS fit] ... It was just the telescopic tube [and the nice box] that I thought would be ideal.

MichaelG.
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Scarodactyl
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Re: Tiny field mcroscope specifically for diatom sampling

#9 Post by Scarodactyl » Sun Apr 05, 2020 8:42 pm

Too big, but this one sure looks nice https://www.ebay.com/itm/264690879312

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