I have a bunch of nice objective lenses from an huge old microscope set, and would like to make a microscope body tube with just one objective and one ocular lens. Without using trial and error to determine the right distance between the lenses, how might I calculate the correct distance between them. I'm then going to make a tube with this length and with a thread so I can mount the objective lenses. For the ocular lens I want to use an adapter from AmScope (CA-NIK-SLR) which mounts directly onto a DSLR camera.

I've tried to use a rolled up paper to determine a good distance from the objective lens to the camera, but I can't tell if the image is focused correctly on the camera sensor. Even if I could tell, I can't easily measure it then. Trial and error for this would take a lot of time and money and so I'd prefer it if I can get a formula or something like that. One of the objective lenses I have

If anyone knows how to do that, I'd be really happy to hear it!

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    $\begingroup$ I would suggest looking for an old Zeiss microscope that someone sell for scrap value. There is more to microscopes than lenses ; the bodies must be ridged, stages must work smoothly, lighting is critical. That looks like a turret type microscope, a good turret would be needed. When I used interchangable objective lens microscopes they had a fairly large handle for ease of changing and they were breech , not thread mount. In use, a single power or difficult to change power would be frustrating. $\endgroup$ May 14, 2021 at 22:05
  • $\begingroup$ Part of the difficulty is that you want to know the location of the field stop, aperture stop, back focal plane, etc. with reference to the mounting flanges. Perhaps you can derive some of these with the help of a well-collimated input beam; then a simple raytrace will show the length of tube between the objective and ocular you want. $\endgroup$ May 17, 2021 at 12:34
  • $\begingroup$ @CarlWitthoft that's unfortunately out of my range. I was hoping for some formulas or international standards that can show me how far apart the lenses need to be. I have a very simple set-up and a low budget. I was able to hold an ocular lens the right distance from the objective for a sharp image, but I wasn't able to measure that distance and the lens I want to use is actually for a camera. $\endgroup$
    – Suryetto
    May 17, 2021 at 13:14


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