MicrobeHunter.com Microscopy Forum

Quick question - on the rotating prism assembly for the B&L trinocular head, p/n 31-18-79, are there supposed to be any optics that move into the path for the camera port?

I'm having trouble forming any sort of image, even using a B&L focusing tube/camera adapter (which should be the correct unit based on the cat. no., but I'm not sure I trust the consistency of their part numbers). I haven't been able to find a diagram or photo detailing the internals of the of the trinocular head, but I did notice a single threaded boss where a lens may have attached to the assembly - and it does seem that the head has been disassembled at some point.

No, just a prism moves with the lever.

Where exactly is this threaded boss?

wporter wrote: ↑

Thu Sep 12, 2019 1:39 am

No, just a prism moves with the lever.

Where exactly is this threaded boss?

Thank you. I figured I had something wrong in the camera setup, but was afraid this scope was missing something critical. I'll keep working on the camera adapter.

Here's an out of focus photo of the boss I mentioned.



The boss is on the prism mount. My fear was that a lens similar to that in the path of the eyepieces was needed.

That is a mounting point for one end of a toggle spring, that provides the two positive setpoints for the prism position, i.e., in the light path or out of the light path. Yours is missing, which is OK, as the lever and prism will still work; they just aren't held in the in or out position very well. Just don't bump the lever in the middle of an exposure and you should be alright.

The critical lens is in the nosepiece, so you shouldn't need anything else in there. I got a microzoom set up, just using a normal stereo eyepiece to project onto the camera. Not the ideal approach but fubctional anyway. I am not sure if they ever made a solution for slrs, though they certainly did for video and polaroid cameras.

wporter wrote: ↑

Thu Sep 12, 2019 6:06 pm

That is a mounting point for one end of a toggle spring, that provides the two positive setpoints for the prism position, i.e., in the light path or out of the light path. Yours is missing, which is OK, as the lever and prism will still work; they just aren't held in the in or out position very well. Just don't bump the lever in the middle of an exposure and you should be alright.

I figured the selector shouldn't be so loose, but I'm not too worried about it now. Thank you.

Scarodactyl wrote: ↑

Sat Sep 14, 2019 12:15 am

The critical lens is in the nosepiece, so you shouldn't need anything else in there. I got a microzoom set up, just using a normal stereo eyepiece to project onto the camera. Not the ideal approach but fubctional anyway. I am not sure if they ever made a solution for slrs, though they certainly did for video and polaroid cameras.

Any details on your setup to help get me going in the right direction would be appreciated.

I worked a bit more on the setup I have and it is definitely the wrong variation of the B&L focusing tube. The main part number matches the one shown in the Cambridge era Microzoom II manual (42-12-55-57, part of the AX-1 automatic exposure controller system), but is lacking the last set of digits (mine is marked only 42-12-55). The entire field of view of the camera is filled with soft uniform color of the specimen, but no matter the extension I use between the camera and adapter, or between the head and focusing tube, I can't resolve any detail. I suspect the relay lens (??) at the base is different from what is needed for the Microzoom. My next step will be to start playing with eyepieces and extension tubes.

I don't remember all the details unfortunately, but I had an empty tube I got as part of a microscope parts lot, no optics just the right 1 1/8 inch tube at one end and a 23mm eyepiece hole at the other. I put an eyepiece in and used a standard 1 inch clamp adapter to put a dslr over it. It worked better than that should work.
Now that I think of it that scope also came with an adapter with a lens in it. Not sure what else is needed for that, but if I can find it next week I can send it your way.

Scarodactyl wrote: ↑

Sat Sep 14, 2019 1:43 pm

I don't remember all the details unfortunately, but I had an empty tube I got as part of a microscope parts lot, no optics just the right 1 1/8 inch tube at one end and a 23mm eyepiece hole at the other. I put an eyepiece in and used a standard 1 inch clamp adapter to put a dslr over it. It worked better than that should work.
Now that I think of it that scope also came with an adapter with a lens in it. Not sure what else is needed for that, but if I can find it next week I can send it your way.

If you come across it, that'd be great!

I don't know how I didn't put it together earlier, but I had stumbled across your for sale post while searching for any details on the Microzoom. I'm going to give building an adapter another go next week and will try to scale your photos to get an approximate length as a starting point for the tube. I figure that if I incorporate a helicoid, the measurement wont be too critical.

I also got some brass 1 1/8 inch sleeves that I was planning to make an adapter to m42 with (on a stereozoom 6, which has the same photo port). They are just a bit too big but within sandpapering range to fit right in to the photo port, and their inner diameter would accept a press fit male c mount adapter with the threads filed down. From there it is easy to mske an afocal adapter or pretty much whatever you want. Unfortunately the sz6 I had it all planned for ended up being moldy and I had to send it back before making the adapter, but I can send one of those brass sleeves with the other adapter if you want to go that route.

That'd be awesome. A brass sleeve would definitely be a "cleaner" solution than the tube I'd end up cobbling together from random aluminum scraps and m42 extension tubes.