This is a problem I've recently run into while setting up my dad's microscope. You have a nice SZ7 with a trinocular port, but you're not sure how to attach your dslr to it. 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 10x eyepiece at the top, and a standard microscope to camera adapter with a ~1" clamp--this won't work on one of those.
But most SZ7s seem to come with the later trinoc mount. This one does not have any threads--instead it accepts a 27mm tube that is held in place with two set screws. It looks like this:
I think they mostly mounted polaroid cameras on these, so while there are adapters of various sorts available on the used market I don't think any of them would be suitable for a dslr. From my own pervious searches I had only found a guide for mounting a camera for direct projection (just hooking it up with no intervening optics). From my own experimentation this can be done but the parfocal image is much smaller than an aps-c sensor. So generally what you want it something similar to the original style trinocular port, with an eyepiece.
As it turns out, optically both types of trinocular port are the same, they just have different mounts--so all you need to do is mount a 10x b&l eyepiece the correct distance above the port (5 inches), and then a camera the correct distance above the eyepiece to get a good image. So what's needed is an adapter from a 27mm tube to a standard thread diameter (ie m42), appropriate spacers and something to hold the eyepiece at the correct height.
What you need:
A bunch of M42 spacers, order 4 of those sets of three just to be sure (~$3.50 per set $14 total)
An M42 female to C-mount Male adapter (~$15)
a 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
Total estimated cost ~80ish dollars, depending. That is sort of a lot for an improvised solution, but given what a commercial one costs (eg https://www.martinmicroscope.com/produc ... icroscope/
) it's not so bad.
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 27mm. These are available very inexpensively, here is one for example.
They fit perfectly in the trinoc port. Also conveniently, the inner diameter of 25mm is just about the diameter of a standard c-mount. A standard c-mount to m42 adapter almost fits right inside.
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 grinder because it's faster)
A bit of JB-weld and they're stuck together forever, and you can now attach stanard m42 spacers and dslr adapters to the port. You'll typically need a male-male m42 adapter as well to get the threads aligned right, 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.
So just attach an appropriate length of m42 spacers between these two parts. It is about 5 inches, but you can tell you have it right when the image in the eyepiece is in focus. I found I got close enough by using normal spacers, but it could be improved by adding a helicoid for fine-tuning, as it is pretty sensitive to getting this length correct.
Then just add more spacers above with another helicoid and an appropriate m42 adapter for your camera, and you're good to go!
Yup, it's awfully tall, but it doesn't seem to have any problem being tilted a bunch.
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.