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PostPosted: Fri Jan 25, 2019 6:51 pm 
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Joined: Thu Apr 05, 2018 1:06 am
Posts: 243
Location: Idaho
With correction collar. This is a late 1920s antique, based on the serial number fairly close to my 95x fluorite and some brass achromats. It has the same "Chinese hat" lower element cell as achromats and fluorites from this period. Obviously, it isn't coated, but my vintage fluorite from the same period gives a good image with decent contrast.

This is the seller I bought my set of three AO - Spencer apochromats from.

Based on what he did when offering the three apo objectives, if no one bids he will most likely relist it with a lower opening bid.

https://www.ebay.com/itm/Spencer-Apochr ... :rk:1:pf:0

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Rick

A/O 10 Series Microstar
A/O 4 Series Microstar
A/O 4 Series Phasestar
A/O 4 Series Apostar
A/O Cycloptic Stereo
Several old monocular scopes in more or less decrepit but usable condition


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PostPosted: Fri Jan 25, 2019 10:54 pm 
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This is a buy it now and I know the seller. He takes impeccable care of his scopes and objectives.


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PostPosted: Sat Jan 26, 2019 3:31 am 
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Location: Santa Cruz, CA
For those of you who own a similar objective, how would it compare to more modern 40x finite objectives? Say, for example, an Olympus 40x SPlan at .70NA?? Or a Nikon 40x Fluar at .75NA? I know the the newer objectives would have a much wider fields (around 26mm). Much higher contrast as well? Does the extra .95NA of this antique Spencer add significant detail if focus stacking? Or is it more the cool factor of having such a fine if venerable objective that would make it desirable?


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PostPosted: Sat Jan 26, 2019 4:28 pm 
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I don't have that much experience with the older objectives. The ones I have used from AO or B&L were quite impressive although the FOV was significantly smaller. It also required more effort for light optimization. I found myself in awe over the optical quality of such old objectives. Would I use them for stacking etc? No, but only because I have more modern set-ups for my DSLR. For my macro set-up I have not tried a 40X objectives, as my subjects tend to be insects, and I have yet to need such a high magnification. Others on this forum have much more expertise with the older objectives.


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PostPosted: Sat Jan 26, 2019 5:13 pm 
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Posts: 152
Location: Pinehurst, Texas
PeteM wrote:
For those of you who own a similar objective, how would it compare to more modern 40x finite objectives? Say, for example, an Olympus 40x SPlan at .70NA?? Or a Nikon 40x Fluar at .75NA? I know the the newer objectives would have a much wider fields (around 26mm). Much higher contrast as well? Does the extra .95NA of this antique Spencer add significant detail if focus stacking? Or is it more the cool factor of having such a fine if venerable objective that would make it desirable?



Apochronaut, our resident expert or authority on all things Spencer and American Optical would be the logical one to whom to pose such questions, but good luck finding him around here on a weekend.
I own an example of that objective, as well as its big brother the 3 mm. I also own a later version of it. I'm certainly no authority, and I have never used any of the other lenses you mention, but I'm happy to give you my comments.

Firstly that's an apochromat objective - just about as fully corrected as it was possible to make at the time. If you use it with a fully corrected or achromatic condenser and one of Spencer's compensating eyepieces, you will enjoy images without any color fringes. You must use the compensating eyepieces with it because part of the correction for the objective is in the eyepiece.

As has been said, the field will not be as wide as in more modern lenses, but also it will not be quite as flat overall as a plan either. And the later versions of that lens which came coated seem to give a brighter image to my old eyes. Still, due especially to the correction collar and the high numerical aperture you are likely to get just about as good a visual image, if you have everything adjusted correctly. It takes a bit of practice to use the collar properly while the lens is mounted on the scope. As for photographic work, I really couldn't say since i have no experience there. I will note, however, that at the time that lens was manufactured, apochromats were considered the best for color photography under the microscope.

When I first got mine, I didn't have any compensating eyepieces for it, and all I had was the standard two element Abbe condenser that came on my Spencer series 13. I couldn't see much improvement over an ordinary achromat objective. Then it occured to me to dig out the pair of Spencer Planoscopic eyepieces I had purchased earlier and use them (an old book from the early forties recommended such eyepieces for higher powers and na.s.) Even though not compensating, they were quite an improvement. Better condensers later on helped even more.

I use that lens on both my Research models #3 and #5 - they are completely set up for apocrhomats, with compensating eyepieces and fully corrected condensers etc. So I get pretty nice results from that lens, even though it isn't par focal with most of my other objectives which are newer vintage.

That is indeed kinda pricey for such an old lens, and to me it would not be a very a good buy at that price if I didn't already have the eyepieces for it, but this seems to be an exquisite example of such judging from the seller's photos. I have purchased several items from him in the past, too, and they are always as good as they appear to be.

Jim


Last edited by apatientspider on Sat Jan 26, 2019 5:29 pm, edited 1 time in total.

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PostPosted: Sat Jan 26, 2019 5:21 pm 
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Posts: 243
Location: Idaho
The most modern objective I could compare this to was made in the late 1950s for the 4 Series microscope. The more modern objective has a bit better contrast, but that can largely be compensated for by carefully adjusting the illumination. The old uncoated objectives need an illumination source with a field iris that can be stopped down until it almost cuts into the field of view. That, and closing the condenser iris just a bit more than would be needed for a modern objective gives contrast good enough for my purposes.

The antique objective will have more field curvature than a modern one, but the image area in the central field area can be about as good as a modern objective of the same NA will deliver. I have an antique Bausch & Lomb brass 1/6-inch objective (roughly 45X or so) with a 0.85 NA. It's so old it's marked for 160mm tube length because B&L was still making objectives for the older 250mm tube length. It works very close to the cover slip, and can resolve punctae in diatoms on the 8 form test plate as well as any of my more modern objectives of similar magnification.

The microscope being used probably has some effect on image quality from an antique objective, too. My AO Spencer 4 Series seems to play well with the antique objectives. The image quality seems as good as I can get with the original antique monocular stands, even a bit better for me because being able to use both eyes seems to help get a slightly better image. The Cat. 146 wide field (semi wide field by modern standards) eyepieces seem to work well with the antique objectives. Some of the antiques have poor image quality at the edges of the field because they weren't designed to work with wider fields than huygenian eyepieces deliver. But some of the other antique objectives work surprisingly well with these eyepieces.

Sometimes I install my antique brass objectives on the nosepiece and use some cheap imported huygenian eyepieces just to give them a little use. For recreational viewing I think they're not bad at all.

_________________
Rick

A/O 10 Series Microstar
A/O 4 Series Microstar
A/O 4 Series Phasestar
A/O 4 Series Apostar
A/O Cycloptic Stereo
Several old monocular scopes in more or less decrepit but usable condition


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PostPosted: Sat Jan 26, 2019 5:59 pm 
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Posts: 2703
Location: Houston, Texas
PeteM,

I don't have Spencer apo, but paid about $100-$120 for my LOMO apo 40x 0.95. Zeiss / LOMO versions are prone to delamination, so I did not have many options for good copies.

That NA 0.95 will help, if you are stacking diatoms or other highly detailed subjectives that demands high resolution. But for $125, if you don't mind oil immersion, you are better off buying a good copy of Zeiss 40x NA 1.3 (? Not sure about the exact max NA) iris objective.

That extra aperture / resolution also helps for photography, because diffraction matters big time (for resolution) at 40x objective. Do a 100% crop of photo capture, you may see difference between NA 0.85 (and up) vs NA 0.75. Even NA 0.95 for 40x objective is deep into diffraction (even NA 1.3 is not overkill for 40x objective).

Visually (with eyes over eyepieces) though, with a not so detailed live protists, you may not see much difference.

You should be able to add contrast with RAW files and some digital enhancements. Or stop down with condenser iris to about NA 0.8-0.85, to reduce glare.

And yes, as others said, planarity is not great. But if you stack, many times you don't need great planarity.


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PostPosted: Sat Jan 26, 2019 7:18 pm 
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Joined: Tue Dec 06, 2016 6:22 am
Posts: 566
Location: Santa Cruz, CA
Thanks Fan, Rick, Jim, and Einman for your responses.

I have some pretty decent objectives, have never played around with an pre-modern-coatings Apo, but know that many love them.


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PostPosted: Sun Jan 27, 2019 7:18 pm 
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Posts: 2638
Only thing to add is that recently I did some testing with various examples of fixed tube 10X objectives that I currently have on hand. The reason was to find the best compatible eyepiece I have on hand for each objective, compatible for the best possible photo image, that is.
I ruled out, huygens , kellner and ramsden eyepieces, zeroing in primarily on dedicated photo eyepieces from Nikon, Kyowa,Olympus,Wild, Jena, B & L , various compens eyepieces, as well as some proprietary flat field or plan types.
I ended up with 60 or so 10X objectives imaged through about 20 different eyepieces of 2.5X to 10X magnification. I used a fixed set up on an adjustable graduated eyepiece tube, with the eyepiece projecting direct to the sensor. The coverage in each case was adjusted to be an equal portion of the slide.

In the 10X magnification, I have Spencer apochromat objectives from 5 incarnations. They are all built for 160mm tubes but they break down into 2 physical styles. The earliest , dates from about 1900 or so and is quite long, about D.I.N. length. The next oldest , physically looks the same , with a very broad front lens and a similar barrel but is much shorter; more of the 34m mm parfocal size. It dates likely from about 1910 or so. The last 3 look almost identical and are of the 34mm parfocal type. One dates from the early 1920's, one from the late 40's and a coated version dates from the mid. 50's. The 4mm objective noted in this thread dates from about 1920, possibly a little earlier

I also have quite a few 10X compens eyepieces made by Spencer. Some came on microscopes to which the objectives were fitted and some came singly.

What I found out was that the characteristics of the apochromats morphed slightly over the years. For instance, a 10X compens eyepiece from around 1925, is not the best match for a 10X apochromat from 1955 and visa versa.The incompatibility results in very slight yellow/blue chroma showing up visually here and there with many samples; less with some but it is more severe when photographed.
I take this to be a normal historical development based on changes in glass formula availability, design theory and the subsequent improvement in the lens. All of the objectives from 1920 on , look virtually identical but they do require matching compens eyepieces from the same period, for best performance, especially if being used for photos.

I could find no Spencer compens eyepiece to work well with the turn of the century 10X apochromat, nor could I find any from any other maker . All yielded a poor level of yellow/blue banding around various elements of most unstained slides. I did however get good results from a couple of the photo eyepieces; the Kyowa 2.5X was excellent, as was the Wild 6X K.

Point is. If you are setting up a photo system, or even if you are not, don't assume that all compens eyepieces are created equal

even within a specific manufacturers production.
=======================================

In order to get a high level of correction from older apochromat objectives, they need to be carefully matched with the correct eyepieces.


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