MicrobeHunter.com Microscopy Forum

I went to another surplus sale today--the big find was a really nice brightfield/darkfield base for my dad's SMZ10, but I also picked up this older AO/Spencer scope. I barely missed out on a really nice trinocular Leitz, though that's probably for the best given my limited desk space (and my brother/housemate's limited patience with my optics habit). I assume this isn't particularly rare, but is anyone familiar with this model? It doesn't seem to have any labels beyond the maker's marks.





I absolutely love the fact that the Apo objective is gold. I wish that were still standard!
The one thing it's missing is lighting. I gave it a quick try with my phone's LED and everything seems to be in order, but I'm curious what kind of lighting it's supposed to have.

Looks like a 15 series scope. Take a look at this, page 15:

https://user.xmission.com/~psneeley/Per ... d35Cat.zip

Lighting options are varied, mirror reflected, simple ac illuminators, and even Kohler capable using the more advanced illuminators like the 735 or 370. Page 18 of the above referenced catalog.

Nice scopes and fun to use.

Rod

_________________
Rod Nabholz
http://www.homebuiltastronomy.com
http://www.wildsideiowa.com

Thanks, that's the one! Though I guess this one must be a bit later since it has a quadruple nosepiece, and I don't see the apo 43x listed. I wonder if I should try to track down an authentic illumination system or if it would make sense to install something more modern. I'm honestly not sure if I'll keep this one long term but it's a nice attractive little scope and it doesn't take up much space.

The original illuminator was a 110/115 v. 15 watt housing , coupled directly to a 1.25 abbe condenser. The illuminator stayed with the condenser as it rode up and down it's focus track. It was controlled by a simple on off switch on the cord.

Since the eyepieces are 10x compens , as well as carrying a nosepiece designated for a 2mm objective, the microscope was originally set up with an apochromat optical complement, however 3 of the 4 objectives have been replaced with achromats. The compens eyepieces correct well with achromats only over the central portion of the field, being too undercorrected at the periphery, therefore yielding considerable chromatic aberration. In it's current state, the imaging with 3 of the objectives will be poor. You would be well advised to keep your eyes peeled on ebay and try to find the other 3 apochromats (10,20 and 90x).
That would elevate the imaging of the microscope to fine, from unacceptable.
AO/Spencer apochromats often sell quite cheaply these days.

The illuminator is going to be harder to find. There was one languishing on ebay for a couple of years. The seller had unrealistic expectations of it's value but perhaps they have had a revelation, lately. I will look.

What exactly is under the stage? Could you post a picture?

Sure, here are a couple more pictures.


I've looked at a few prepared slides I got in an old collection of stuff, but I can't say that the actual image quality seems particularly good even on the apo objective. To be fair that is with a too-small LED light under the condenser which might be totally wrecking it.
I also gave it a try in ultra widescreen mode:

(As is obvious this is a terrible idea).

No mirror, so it was probably used over an ortho illuminator. You have the 1.30 achromat condenser. I would be looking for the rest of the apochromats.
Did the FJW Industries eyepieces come with it as well as the 10X compens? Those are very useful in an application where their wide field and relatively high resolving power is valuable, as long as the objective is compatible. Probably, they do o.k. with the 10x and 43x achromats but not so, with the 4mm apo. Those little button 3.5X suffer from lateral c.a. anyway. The FJW are actually Bausch & Lomb eyepieces and their best use is with a stereo mic.

The 15x uwfs came with a B&L zoom 240 (and I use them on my SZ7), I just put them on as a goof. The resultant image is very poor, with a lot of what seems to be empty magnification.

Yes, the image would not be great but not due to empty magnification. Those are non corrective eyepieces, designed to magnify an otherwise perfectly corrected image 15X, with a very wide f.o.v.
You will get considerable chromatic aberration with relatively uncorrected finite tube objectives but also other aberrations the more you look off axis. Those work well with any microscope that produces a fully corrected image to the eyepiece. They are high resolution, ultra wide field 15x magnifiers only.

None of the objectives you have there would be prone to empty magnification with any 15X eyepiece based on the simple rule that the product of the objective mag. X eyepiece mag. must not exceed 1000 x N.A. In the case of your objectives, the 4 ratios are : 35/90 , 150/250 , 645/660 and 645/950
The 43X is closest but it is easy to see in this case, just why microscope optical engineers zeroed in on .65 or so as the optimal basic N.A. for most professional grade microscope 4mm objectives. 4mm objectives, depending on the lens designers optical formula are any where between 40 to 45X magnification , when used with a 160mm tube. Setting the N.A. at .65, gives the possibility of using a 15X eyepiece, instead of adding in a 3mm objective, while allowing for a decent w.d. and fine enough resolution to do most work. Quality manufacturers, further , produced 15X eyepieces of an advanced design, that did not introduce field restrictions. Many cover a field very close or in the case of those FJW, equal, to the actual field covered by a 10X eyepiece.
15X eyepieces were seldom intended to be used with standard achromat objectives over 4mm( 40-45X), nor would standard achromat objectives over 4mm, indicate such use. There are a few exceptions of very high N.A. achromats being made, often as 3mm(60-63X), where N.A.s of 1.0 to 1.25 can be found. In the case of apochromats, with N.A.s often double those of achromats, the use of 15X eyepieces across the board was usually normal. Spencer and Bausch & Lomb for instance produced 15X eyepieces as the default eyepiece with their apochromat systems. They were designed with the widest field and superior eye relief. In the case of the higher power oil immersion objectives, they deliberately limited their magnification a little, to 2mm or around 90x at 1.30 or 1.40, instead of the more common 1.8mm or 100X at 1.25 for an achromat, in order to facilitate a greater, highly resolved magnification.
90 x 15 = 1350 : 1.30 x1000 = 1300. While this may seem to exceed the rule, in the case of apochromats the upper threshold is slightly higher due to the extra wavelength correction designed into apochromats. With modern ones, it is probably even higher.

That does make sense--what I was seeing wasn't chromatic abberations (though there was plenty of that of course), but something worse, bad blurring of details etc. But I just tried again with slightly better lighting and different slides and it performs just fine even with the wrong eyepieces, about what I'd expect from an older scope, so I assume either the lighting was worse than I thoguht the slides I was testing with yesterday are badly dried out/delaminated and I didn't notice. All my prepared slides were purchased as part of an estate, some professionally prepared samples and some self-prepared, and I must have just grabbed from the wrong box. I'll have to dig through them again to find which ones I was using.
(Edit: it was the bad slide causing trouble. Using a good slide it performs just as good as I'd hope for).