phototube/ Nikon DSLR adapter for AO Series 10

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toomanyhandles
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phototube/ Nikon DSLR adapter for AO Series 10

#1 Post by toomanyhandles » Tue May 04, 2021 10:53 am

Hi all;

I have obtained a trinoc head for my AOSeries 10, and am looking for best options to mount my NIkon DSLR. I don't want to use a C-mount camera for multiple reasons. I have both DX and FX Nikon SLRs available, but would prefer to dedicate a DX body.

What is the best way to be as parfocal as possible?

I see adapters like this:
https://www.ebay.com/itm/152323422958

and while I read about using an eyepiece as a relay lens- this adapter's size doesn't seem right to drop an eyepiece _into_ it.
Assuming this is an appropriate adapter (same seller has a different one for C-mount) I'd be looking for a F-mount adapter that would go over the eyepiece, but so far I only see ones that replace the eyepiece- which isn't right for microscope use. e.g. https://smile.amazon.com/Solomark-Camer ... B07DYJMP37

I feel like I'm missing an entire category of F mount adapter and phototube somehow. I don't see any #1044 available at this time, but did find the measurements here: http://user.xmission.com/~psneeley/Pers ... otube2.JPG and photos of setups with a DSLR on the trinoc are not uncommon on the forum....

Something like this: https://www.amazon.com/AmScope-CA-NIK-S ... B005OZ4BME
should work but this also looks like it replaces the eyepiece, so instead of 10X or 15X I'd be at 2X (but what they call 2X is I think just cropping) plus the objective magnification?

Brian.

apochronaut
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Re: phototube/ Nikon DSLR adapter for AO Series 10

#2 Post by apochronaut » Tue May 04, 2021 12:21 pm

The DX has a smaller APS-C type of sensor, and the camera body itself is a bit smaller, so it is probably your better choice. A full frame camera requires quite a bit more extension so the trinocular tube becomes a bit of a top heavy tower contributing to the already existing risk of excessive vibration from a large camera.

So, of the options you provided links to, the last one is pretty much useless and the second one could work but it would be hard to find a properly corrected optic to use with it, that would not restrict the f.o.v. and or be parfocal.

Option 1 is a possible start but with the following qualification. The original AO photo tube has a baffle at the opening that blocks reflection at the front aperture. The original versions of those knockoffs did not, and allowed a lot of flare causing a huge loss of contrast and hotspots in the image. I noted this problem to the seller, over a year ago and I am not sure he has redesigned the tube to include a baffle. It is easy to tell if the tube works. If you look down the original tube all you see is a dark tube with a bright hole at the end. If you look down one of the defective knockoffs, the tube is brightly illuminated from reflection, even though the tube is in fact blackened internally. You can repair it by putting flocking on the lower section, making sure it covers the lower lip, where most of the reflectivity happens. Glueing on a ring of some kind, with the same o.d. as the tube and a just slightly under i.d.would also create a baffle.

Once you have your tube, the #180 eyepiece is a good photo optic. It is parfocal at the top of the tube. From there, you just need to add a camera adapter. I use a mirrorless camera, so I don't have much in the way of vibration to worry about. Probably you won't either. I think you would have a mirror lock? You can mount your camera on the tube or on a separate stand remote from the tube and use something like bellows or a shade hood.
I use an old camera adapter from the 60's, designed to clamp over an eyepiece tube with a T -thread at the other end, then a helical focuser, another T to bayonet. The entire unit clamps on to the upper narrow section of the trinocular tube. Another incarnation that also works well is an adapter similar to the one in your second link but a 1 1/4" telescope version that fits OVER the photo tube. It should have a T thread . Drill and tap it for 3 thumb screws, to clamp on the photo tube. Put a helical focuser on it , then T to your bayonet.

In each case, the microscope camera adapter and the telescope adapter, the throat must be large enough that it allows a #180 eyepiece to fit inside it so it can stay put in the photo tube, when the adapter is slid up and down to get the best location for parfocality. Personally, I don't worry too much about absolute parfocality. The Sony mirrorless has a large screen that can be brought over , just above eye level, so I can use the camera focus magnifier from my position at the eyepieces, which are inactivated for image capture anyway. So I do my final focusing on the camera. I use the same perfect system on all of the AO microscopes from the series 4 on up to the Diastar, just changing the photo eyepiece with each one.

If you find too much vibration, you could opt to hover the camera over the photo lens.

toomanyhandles
Posts: 25
Joined: Mon Dec 28, 2020 3:48 pm
Location: Michigan, USA

Re: phototube/ Nikon DSLR adapter for AO Series 10

#3 Post by toomanyhandles » Wed May 05, 2021 11:15 am

That helps a lot, thank you. Great info about the phototube clone and what to look for.

The adapters I will try:
https://www.adorama.com/cntmnk.html
https://www.adorama.com/cnta1q.html

I will need to make a reducer as this is 1.25", but clearly that will be able to go around the eyepiece being used as a photo relay lens.

And maybe this for the helical focus:
https://smile.amazon.com/SVBONY-Precisi ... B08228SQB9

Brian.

apochronaut
Posts: 4104
Joined: Fri May 15, 2015 12:15 am

Re: phototube/ Nikon DSLR adapter for AO Series 10

#4 Post by apochronaut » Wed May 05, 2021 11:46 am

I don't think any of those are the best choice. If you go the telescope adapter route, you want one just like the microscope version in your second link, above. It has a T thread to the bayonet, so you will have to get a thin T to M42 adapter to put your helical focuser onto, then back to T for the bayonet section. I assume you are going to buy one of the knock off photo tubes?

If you get something like this, it clamps onto the tube and in my opinion is a first choice option. https://www.ebay.com/itm/265139616643?h ... SwQbxgiCHG you then just need a thin helical focuser and an M42 to T mount to your bayonet.

That Asahi mount above is a little different than I am familiar with.....maybe newer or more likely already adapted. The one I use has a smaller thread , something like a 39mm at the top which I had to adapt to M42 for the helical focuser. That one I linked to above may already be a T or M42 on the top. Whatever it turns out to be it is easy to convert to your helical focuser which is M42. T and M42 are both 42mm, just a slightly different thread. You can in fact thread one to the other in a pinch, they just lock up after about 2 or 3 turns. You can buy adapters from one to the other quite cheaply and they are very thin, hardly noticeable.

Helical focuser.
https://www.ebay.com/itm/264767676508?_ ... %3A2334524

M42 to T adapter https://www.ebay.com/itm/324483752878?h ... SwSElgBV53 one way only.

toomanyhandles
Posts: 25
Joined: Mon Dec 28, 2020 3:48 pm
Location: Michigan, USA

Re: phototube/ Nikon DSLR adapter for AO Series 10

#5 Post by toomanyhandles » Fri May 07, 2021 11:46 am

That Ashai adapter looks great, I have a few uses for it.

The helical focus- is a goal to keep this stack as short as possible, it that a downside for the one on Amazon?
I was looking for items at Amazon and similar online shops to help provide predictable delivery window- but for cost and smaller height, the best options I see right now are indeed on ebay and ship direct from China.

Thank you!

Brian.

apochronaut
Posts: 4104
Joined: Fri May 15, 2015 12:15 am

Re: phototube/ Nikon DSLR adapter for AO Series 10

#6 Post by apochronaut » Fri May 07, 2021 2:01 pm

The helical focuser actually doesn't do much in the way of focusing. What it does is adjust the extension tube so you can adjust the size of your image circle.
My preference is to get the image circle just outside of the sensor frame, so I am capturing exactly what the eyepieces are seeing. I move that mount around on a few microscopes (series 4 with multiple phase systems + apochromats, series 20 apo Immersion DF, series 10 dark and bright phase) , so the eyepiece f.o.v. varies between the systems and I can drop in the photo eyepiece of choice and then tweak the image circle size or zoom in for a bit of a crop.
It just makes sizing the image circle and framing that much easier, especially if the mount is mobile.

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