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PostPosted: Sun May 12, 2019 11:07 pm 
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Joined: Sat Mar 03, 2018 9:09 pm
Posts: 314
This is a problem I've recently run into while setting up my dad's microscope. I got him a nice SZ7 with a trinocular port, but I wasn't sure how to attach his camera to it (in this case a canon EOS Rebel XS).
If you have the original sz7 trinocular port that has a threaded hole then what you need is a particular B&L threaded tube that accepts a 23mm eyepiece at the top. This is now just a third ocular, so you can use standard eyepiece adapters for a c-mount camera of choice, or a 23mm projective eyepiece and a standard microscope to camera adapter with a ~1" clamp.
Most SZ7s on the market, however, seem to come with an unthreaded trinoc mount. This one accepts a smooth 27mm tube that is held in place with two set screws. It looks like this:
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Optically it's exactly the same, but as far as I know Bausch and Lomb didn't make an eyepiece tube to fit it. They had a few purpose-specific adapters, I believe mostly for polaroids, which are scarce and probably not useful anyway. This guide is for making your own eyepiece tube, and on top of that how to attach a DSLR to it.

What you need:
A bunch of M42 spacers, order at least 5 of those sets of three just to be sure (~$3.50 per set $18 total) --I'll try to get a tally of how many are used on the final version later
1 M42 female to C-mount Male adapter (~$15)
1 male to male m42 adapter (~$5)
1 m42 helicoid (or 2 optionally) (~20/ea)
1 27mm od 25mm id carbon fiber tube end protector (~$4 for 2)
1 ocular off a broken b&l stereozoom (variable, don't spend much)
1 b&l stereo 10x eyepiece (for testing only, use one from an ocular)
For a DSLR: 1 Nikon 2.5x projective eyepiece (I typically pay about 40 dollars for a used one)
For DSLR: 1 m42 adapter for your camera (~$5)

Total estimated cost ~100ish dollars, depending. That is sort of a lot for a self-made solution, but given what a commercial one costs (eg https://www.martinmicroscope.com/produc ... icroscope/ ) it's not bad--and I suspect the results are as good or better.

For the first part, a 27mm tube to m42 adapter, I found a very handy part on eBay. This is a metal cap that is slipped into the end of a carbon fiber tube to prevent the ends from fraying. Its outer diameter is 27mm and its inner diameter is 25mm. These are available very inexpensively, here is one for example.
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They fit perfectly in the trinoc port. Also conveniently, the inner diameter of 25mm is just about the diameter of a male c-mount thread. A standard male c-mount to m42 adapter almost fits right inside.
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All it takes is a bit of modification to get them to fit together perfectly (this could be done with sandpaper, but I used a bench grinder because it's faster)
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A bit of JB-weld and they're stuck together forever, and you can now attach standard m42 spacers and dslr adapters to the port. You'll need to add the male-male m42 adapter here to get male M42 threads facing up (as most m42 dslr adapters accept a male m42 thread.)
All you need now is a convenient way to hold an eyepiece in the middle of those spacers. As it turns out, the ocular off a b&l stereozoom microscope--any stereozoom, 1-7--fits perfectly inside a standard m42 spacer, well enough that you can just let it sit in there and not further secure it even for a microscope with a tilting base.
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So just attach an appropriate length of m42 spacers between these two parts. It needs to be about 5 inches from the base to the ocular, but you can tell you have it right by getting a nice bright subject under your scope in sharp focus, putting an eyepiece in the ocular and adjusting the length until the image in the eyepiece is in focus. I found I got close enough by using normal spacers, but it could probably be improved by adding a helicoid for fine-tuning, as it is pretty sensitive to getting this length correct.
Once the b&l eyepiece is in focus you can now use a standard eyepiece adapter for your camera of choice. I haven't done much with smaller c-mount cameras so you might be able to remove the ocular entirely and do direct projection with an m42-cmount adapter.
If you want to use a DSLR, put a Nikon 2.5x projective eyepiece in the ocular. Then add more m42 spacers above with another helicoid and an appropriate m42 adapter for your camera. Add/remove spacers and adjust the helicoid until the image in the camera is in razor-sharp focus.
Typically the 2.5x is good for full frame and works on aps-c with a bit of cropping.
Image
The end result looks awfully tall, but it doesn't seem to have any problem with being tilted, and the vibrations aren't too bad.
I suspect the trick with b&l oculars inside m42 spacers should be useful in a number of cases where original adapters are unavailable or expensive.


Last edited by Scarodactyl on Mon May 27, 2019 4:20 am, edited 1 time in total.

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PostPosted: Mon May 13, 2019 7:15 am 
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Joined: Mon Apr 10, 2017 8:24 am
Posts: 1349
Location: NorthWest England
Those 'end protector' tubes look a great find ... thanks for the link.

MichaelG.

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PostPosted: Mon May 27, 2019 4:29 am 
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Joined: Sat Mar 03, 2018 9:09 pm
Posts: 314
Thanks!
I did some more testing, and the b&l eyepiece doesn't perform as well as a projective as I'd hoped from initial tests. However, using a Nikon 2.5x photo eyepiece works great. I've also got a Kodak MDS120 on its way since Einman reported good results with it. We'll see if I can get mine to behave, and how it compares with the Nikon.


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