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 Post subject: A DIY Wild M400 / M420 Macroscope
PostPosted: Thu Oct 03, 2019 8:21 pm 
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Have you dreamed of owning a Wild M400 or M420, but the price was too high? Are you also comfortable buying components on eBay, reasonably handy with a sander and drill press, and willing to do some tinkering?
If so, this might be just the project for you: an economical frankenmacroscope.
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First, a brief introduction to the Wild m400 series macroscopes. These are similar to a stereo microscope, with a long working distances, low magnification, a noninverted image and zooming optics. The difference is they only have one light path right through the middle, rather than two side by side. That means that you don’t get a 3D view, but the optics are higher resolution and free of distortions you get with stereos—not quite as good for inspection, but much better for photography.
The M400 series are excellent and are quite valued on the used market. I have one myself and I use it a lot—it’s just a wonderful tool, especially for gem photography.
So why would you want to assemble one from a hodge-podge of parts from different brands like this? Because they’re usually kind of expensive. An M400 or M420, both of which are pretty easy to convert to accept a modern DSLR, will typically run over a thousand dollars (or much more depending on context). You can get an M450 for a bit less, but it requires a specialized adapter to mount a dslr.
However, the most expensive part is the head/focus mount (which are basically one unit). The Makrozoom lens itself is occasionally available loose at very reasonable prices (they were sold without the full head for industrial use), sometimes 100-300 dollars. This lens is the heart and soul of the system, everything else is just there for support.
I recently won an auction for this microscope head, labeled “ADE Phase Shift”. This is a Nikon OEM head—specifically it looks like an erect-image head from their late industrial Optiphot microscopes (ie the Optiphot 300).
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This is a nice head, but it didn’t fit it on the nikon scope I thought it would. I noticed it had about the same size dovetail as a makrozoom lens, grabbed one and...
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it fits! No modification needed, though it does bite into the edge of the nikon dovetail a bit if you tighten too much.
Better yet, it produces a great image in the eyepieces, and the zoom is totally parfocal if you set your eyepieces up right [I did have to use Nikon eyepieces for that, as the others I tried wouldn’t quite produce a parfocal image. B&L 15x UWF eyepieces produced odd, strong distortion at the edge of the FoV). The parfocality is kind of amazing, because without an appropriate lens above the makrozoom objective it is not at all parfocal. Though this Nikon head was for a finite microscope system (I am pretty sure??) it does have a tube lens in the head, maybe as part of the process that makes the image upright in the eyepieces [EDIT: apparently the optiphot-150/200/300 scopes are infinity corrected, though confusingly described and equipped). Whatever the reason, the head works just the same as an M400 or M420 head would (though this one only has 23mm oculars, so the view through the eyepieces is slightly narrower than you’d get with a real Wild head. The FoV is identical in the camera). It does mean that not just any finite Nikon head will work—it needs to be from this particular series. A normal Nikon finite head has nothing between the objective and the camera but empty space so your image is not parfocal at all.
With the basic fit lining up, I wanted to mount my DSLR on the trinocular port. The M400 is well known for allowing direct projection onto aps-C: the image once it comes out of the head doesn’t need any more magnification as long as you can mount it at the right height. Step one was removing the camera and dorky camera tube that came with the nikon head, then removing the c-mount adapter (a cool one that allows you to rotate the position of the camera by turning a knob! I will probably pass this on to another nikon enthusiast).
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The existing tube here is just a bit too tall. Fortunately it is just held on with three bolts (save the bolts!):
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Those of you who have seen my thread about adapting a dslr onto a Wild m420 might notice how similar this is. Under the tube is a flat plate with a ~25mm hole and three threaded holes, just like you’d see under the photo tube on an M420. Adapting a camera mount to this is just as easy, because:
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The diameter of the hole is just slightly smaller than a male c-mount, so a male c-mount to female M42 adapter forms a great basis for an adapter. All you need to do is grind the threads down just a little bit (I used a flexshaft but plain sandpaper would work), and then drill three holes to allow the bolts off the original photo tube to fit through.
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The adapter fits right into the head and screws on. [Note: I haven’t yet done this, but you’ll also want to flock the inside of that black tube to avoid internal reflections. Peel-n-stick flocking paper is not that expensive, and after rolling over it with a lint roller to remove loose threads should be a good solution. If I have any problems I’ll update this note).
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Once you have the adapter on, an aps-c (crop sensor) camera can be mounted with a male-male M42 adapter, empty adapter tubes and an M42-to-your-camera adapter. Including a cheap chinese M42 helicoid will allow you to finely adjust the height to get perfect parfocality with your eyepieces. You can also leave one of the threads loose so you can rotate the camera, which is very handy.
With the optics sorted out, all that’s left is mechanical stuff. First, we need something to hold the head, and then we need a coarse and fine focus mount (just a coarse focus would not be great for high magnifications).
On an M400 the focus mount is screwed directly onto the head, which isn’t an option here. Instead, I decided to mount it like a stereo microscope, held in a ring with a set screw.
The Makrozoom objective is about 85mm across, and a Meiji stereo microscope holder is 84.2mm:
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It’s so close to fitting, and with some work with my flex shaft and some sandpaper I was able to widen it out to accept the objective (don’t use a flex shaft with a diamond bit for this, it takes forever and there must be a better way). It would probably be smarter to make an adapter to fit the objective in an American Optical stereo star mount (4 inches/100mm round) or a bausch and lomb (complicated) as they are a bit cheaper than Meiji mounts, but this does look fairly natural.
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With the objective inside and the top flush with the bottom of the Nikon head it is a very secure arrangement.
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Unfortunately the Meiji ring is just a ring, with no focus mechanism [hence why I could buy it for a reasonable price). Fortunately I had a Leica coarse/fine column on hand to attach it to. Those are usually unreasonably priced, but other coarse/fine mounts do come up from time to time, especially Nikon and Olympus ones.
I used an aluminum plate to make my adapter. Step one was fitting it to the Meiji holder, which involved drilling three holes for screws and two for indexing pins:
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Next I had to make it fit the Leica focus mount, two indexing pins and one screw:
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This leads you to a bit of a paradox: if you screw the adapter onto one of them, you don’t have access to the other side, so you can’t screw in the other screws. In this case there was a simple solution:
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By drilling one hole in the Meiji holder I had access to tighten the screw onto the Leica mount.
I attached a second aluminum plate to the bottom of the Leica focus mount, screwing into the three threaded holes and giving it a broader base with four wide holes to accept 3/8 inch bolts.
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This is sort of dumb, but I put it on a nice slab of quilted maple, sanded and varnished. It is easy to work with and will be easy to attach accessories to, plus it looks nice. It is easy to change the base plate, since it is just held on with four well-spaced bolts.
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And here’s the final product, next to its purebred cousin, a normal M400. It may be an oddball, but I think it is a rather fine-looking instrument in the end.
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So, a quick rundown of some pluses and minuses:
Minus: with 23mm oculars you get a smaller FoV, though the FoV in the camera is about the same. It does not have an iris like a Wild, so no ability to stop it down. This project also takes a fair amount of work and scrounging for parts, and you’ll need a drill press at least, and a bench sander helps a lot too. This only makes sense with the Makrozoom objective. The upgraded Apozoom is so expensive and rare that, if you were to find one loose, it would still make sense to just buy an original Wild head. So you'll be stuck with nice but merely achromatic performance.

Plus: This is cheaper to assemble than a real M400 series macrosocpe, tilting and ultrawidefield ocular options are available with these Nikon heads. Look out for Wyko and Zygo heads that look similar, as Nikon did OEM stuff for them too. The head switches between 100% eyepieces and 100% camera, while an M400 or M450 is stuck on a 50/50 split all the time. It’s also a fun project to watch come together.

The big question, though: how does it work? I'd say great! It's easy and comfortable to use and it takes pictures just as good as a full Wild macroscope. These were taken by wirelessly connecting my phone to my camera and with a cheap LED ring light, so you can actually expect better results with more careful lighting and tethered to a computer for better focus stacking.
Click for full size images:
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A beautiful little topaz from Bahia in Brazil, tiny imperials found in hydrothermal veins.
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I thought these were quartz on it like the others, but look at these cute fluorites! Cropped from the above image.

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A faceted topaz, stacked from just three images. This lighting setup is great for showing off well cut stones, because inclusions and scratches show up pretty well.

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A delicious gummy.
Crop from the center:
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A botryoidal overgrowth on green opal we collected a few weeks back on a random gravel road in southern Idaho.
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Look at those beautiful dendrites inside each botryoid.

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