Olympus EHT

What equipment do you use? Post pictures and descriptions of your microscope(s) here!
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piilani2000
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Olympus EHT

#1 Post by piilani2000 » Mon Apr 02, 2018 9:48 am

Hello
I have got my first microscope two months ago and it's an Olympus EHT-431.
EHT
EHT
microscoop.jpg (283.57 KiB) Viewed 3149 times
It's trinocular and a phase contrast microscope. It has an NA 1.25 Abbe Condenser. Currently, I use my phone to take photographs, but I'm planning on buying a T2 ring soon. I do have a T2 ring For a Fujica X and a canon, but we have a Nikon.

On the microscope is a sticker that says 2002. However, I know that the microscope is a lot older. :lol: I found a site that said that the Olympus EHT was produced in 1980 approximately, but I wondered if anyone knows if this is correct.
Olympus EHT

Hobbyst46
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Re: Olympus EHT

#2 Post by Hobbyst46 » Mon Apr 02, 2018 10:00 am

There is a manual for the FHT-EHT microscopes on the alanwood website. It is a PDF file that you can easily download. From the look of the manual and the microscope, I think that it is either late 1960's or early 1970's model. The eyepiece on the phototube is in my opinion a FK photo eyepiece - for photography, using the short barrel objectives. Hopefully it is an FK 2.5x. These short barrel objectives are of a parfocality distance of 36mm, the old Japanese standard from that era. You can find their exact designations and function in the manual or on the alanwood site. I guess some of them are phase contrast, but for phase contrast you need an appropriate condenser. More modern Olympus scopes use the long barrel 45mm parfocality objectives. The illumination is probably an incandescent bulb.
Congratulations for a beautiful, well maintained, enjoyable microscope!
Last edited by Hobbyst46 on Mon Apr 02, 2018 10:08 am, edited 1 time in total.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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piilani2000
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Re: Olympus EHT

#3 Post by piilani2000 » Mon Apr 02, 2018 10:06 am

Yes, I did find that site, too. Really helped a lot! I learned how to use the iris diaphragm for example. I just looked and the eyepiece on the phototube has PH2,5X. Is that the same as a FK2,5X?
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Hobbyst46
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Re: Olympus EHT

#4 Post by Hobbyst46 » Mon Apr 02, 2018 10:25 am

piilani2000 wrote:I just looked and the eyepiece on the phototube has PH2,5X. Is that the same as a FK2,5X?
Sorry, I do not know. Perhaps the Ph2,5x is not Olympus but some other brand that was tried and found to be satisfactory. Perhaps you can post a question to Alan Wood. Anyway, you can first of all check if the photo eyepiece and viewing eyepieces are parfocal. Take a speciment slide, focus by looking through the bino and verify that accurate focus remains when you look through the photo eyepiece. If they are, you have a good start. Then you can find expert, excellent directions regarding the installation of a modern camera on the scope, on this forum, on the Charles Krebs site and elsewhere.

BTW, on pages 15-16 of the manual you find the instructions to set Kohler illumination, including alignment of the light bulb with the knobs on the lamp socket. That part of the operation is basic and important, to be verified at the beginning of nearly every session.
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piilani2000
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Re: Olympus EHT

#5 Post by piilani2000 » Mon Apr 02, 2018 10:52 am

Thank you so much for your tips and advice, Hobbyst46! I am gonna look at page 15 and 16. I don't think that they are parfocal because when I look through the photo eyepiece I have to focus again. How important is it for the photo eyepiece to be parfocal?
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75RR
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Re: Olympus EHT

#6 Post by 75RR » Mon Apr 02, 2018 11:28 am

How important is it for the photo eyepiece to be parfocal?
Very!
I don't think that they are parfocal because when I look through the photo eyepiece I have to focus again.
Most microscope photo tubes can be adjusted up and down via a thread.
I can't tell by the photo or the manual but there 'should' be a way to unlock it. (Perhaps turning the silver ring)
If it does, you will then probably find that it can be screwed in or out about 10mm, which is usually enough to focus it.

As to the bulb filament, once it is focused and centered there is no need to redo these steps again unless the light is detached or the bulb is replaced.
You will however have to achieve Köhler every time you change objectives, as it improves the image.
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Re: Olympus EHT

#7 Post by Hobbyst46 » Mon Apr 02, 2018 12:01 pm

Perhaps you would like to take a look at
https://digital.lib.ecu.edu/22096#details
showing a similar microscope, with a phase contrast condenser.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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piilani2000
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Re: Olympus EHT

#8 Post by piilani2000 » Mon Apr 02, 2018 12:25 pm

piilani2000 wrote:I can't tell by the photo or the manual but there 'should' be a way to unlock it. (Perhaps turning the silver ring)
I will look if it can be done! I didn't found something in the manual either.
piilani2000 wrote:As to the bulb filament, once it is focused and centered there is no need to redo these steps again unless the light is detached or the bulb is replaced. You will however have to achieve Köhler every time you change objectives, as it improves the image.
Alright! Will keep this in mind. Thank you.
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piilani2000
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Re: Olympus EHT

#9 Post by piilani2000 » Mon Apr 02, 2018 12:26 pm

75RR wrote:Perhaps you would like to take a look athttps://digital.lib.ecu.edu/22096#detailsshowing a similar microscope, with a phase contrast condenser.
Wow, that's the one I have! Thanks :)
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apochronaut
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Re: Olympus EHT

#10 Post by apochronaut » Mon Apr 02, 2018 1:00 pm

Hobbyst46 wrote:
piilani2000 wrote:I just looked and the eyepiece on the phototube has PH2,5X. Is that the same as a FK2,5X?
Meiji made a ph 2.5X . "ph" just stands for photo and there are also many generic ones out there, similarly marked. Objective lenses, such as yours have some unique characteristics , which need a degree of compensation in the eyepieces. You may find that the " generic" photo eyepiece does not correct properly towards the extreme perimeter of the image; hopefully it does but if not , that and the parfocality differential will be overcome by putting in the correct photo eyepiece..

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piilani2000
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Re: Olympus EHT

#11 Post by piilani2000 » Mon Apr 02, 2018 1:10 pm

piilani2000 wrote:that and the parfocality differential will be overcome by putting in the correct photo eyepiece..
Hmm... that's unfortunate. Thanks for the information :) !
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Re: Olympus EHT

#12 Post by 75RR » Mon Apr 02, 2018 1:13 pm

Link to original spec photo eyepieces: http://www.alanwood.net/photography/oly ... copes.html
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Re: Olympus EHT

#13 Post by Hobbyst46 » Mon Apr 02, 2018 1:35 pm

Wow, that's the one I have! Thanks
Notice that the phase condenser in the Digital Collection site has numbered positions: 10, 20 etc. These refer to phase objective.

About the photo tube:

Luckily, the EHT microscope takes an FK, rather than an NFK photo eyepiece. The latter type are rare and very expensive. You may find an FK5.0x, it is still compatible with your optics though not optimal with respect to the image size.
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piilani2000
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Re: Olympus EHT

#14 Post by piilani2000 » Mon Apr 02, 2018 2:32 pm

75RR wrote:Link to original spec photo eyepieces: http://www.alanwood.net/photography/oly ... copes.html
Thanks for the site! Didn't know that there are so many photo eyepieces. Alanwood is great.
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Re: Olympus EHT

#15 Post by piilani2000 » Mon Apr 02, 2018 2:35 pm

Hobbyst46 wrote:
Wow, that's the one I have! Thanks
Notice that the phase condenser in the Digital Collection site has numbered positions: 10, 20 etc. These refer to phase objective.

About the photo tube:

Luckily, the EHT microscope takes an FK, rather than an NFK photo eyepiece. The latter type are rare and very expensive. You may find an FK5.0x, it is still compatible with your optics though not optimal with respect to the image size.
Ah I get it! And yes lucky that's not the NFK then. I hope to find a FK then one day!
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MicroBob
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Re: Olympus EHT

#16 Post by MicroBob » Mon Apr 02, 2018 5:01 pm

This is a really beautiful microscope you've got! Trinocular heads are quite rare and so it is great that you alredy have one. I don't like microscopes in hospital-beige colours. Black is nicely scientific but this grey look also great. I have an inverted microscope of this era from Olympus.

When you look for a photo eyepiece you could look in two directions:
a) an eyepiece for direct projection on the cameras sensor
b) an eyepiece to be used with a relais optic on the camera. Here a normal eyepiece for use with glasses is fine and a pancake lens on the camera

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Re: Olympus EHT

#17 Post by piilani2000 » Mon Apr 02, 2018 8:00 pm

Thanks microbob.
MicroBob wrote:Trinocular heads are quite rare
I didn't even know that they existed. And now I'm really glad I have one.
MicroBob wrote:I don't like microscopes in hospital-beige colours
I totally agree! Black is the best color. But this grey is actually okay too! And an inverted microscope!!! So awesome. Never seen one.
MicroBob wrote: When you look for a photo eyepiece you could look in two directions
I think i will go with option A. I already have a photo eyepiece and adapter! Only needing a t2 ring :). Thank for the information! Really appreciate it.
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