Are cheap 100x objectives any good?

[ChrisR]

Has anyone tried the <$20 objectives from China at this magnification? Some are as low as £12.

"My" secondary school doesn't have any objectives over 40x/0.65, which isn't enough to look at chromosomes etc.

There are 60x /0.85s, but I think they'd be better off going to 100/ 1.25 oil.

Their microscopes are basic but competent, fairly modern finite school models, with critical rather than Köhler illumination.
As such I don't think they would use compensating eyepieces.
They only need a couple.

I'm not sure if theirs are DIN - I don't think it would matter.

Tried this on photomacrography.net / amateurmicrography.net, 72 views and no answers!

[Crater Eddie]

I never tried one of those super cheap ones because it just sounds "too go to be true". And such things usually are. I tried a cheap Amscope objective in my LOMO and Olympus scopes a year or two ago and ended up sending it back.
One of our other group members here has had some experience with those objectives, perhaps he will chime in.
If you can send it back then why not try it out and see? All you are out is some time and maybe shipping. If you do, be sure to report here.
CE

[ChrisR]

Thanks Eddie. Shipping to China would mean it wouldn't be worth sending back.
Maybe a cheap Lomo or something would be a better bet, but the school folk might decide they want more.
I have an old type Olympus (black knurled ring) but that definitely needs eyepiece correction.

[75RR]

I have an old type Olympus (black knurled ring) but that definitely needs eyepiece correction.

If you are looking for structure, then perhaps the residual chromatic aberrations that the compensating eyepieces correct for would not be critical. Maybe you can do a test to see if the resulting image on the student microscopes is acceptable enough.

[billbillt]

I have used these cheap Chinese objectives with OK results... But, I am not as persnickety as some are.. I can easily live with less than 100% perfection.. Just my HO....

BillT

[MicroBob]

Hi Chris,
it is no wonder that nobody has answered your question on PM - it is difficult to make out what you really want.
I will try it.

"My" secondary school doesn't have any objectives over 40x/0.65, which isn't enough to look at chromosomes etc.
Why, the chromosomes in onion tips can be seen with a 40:1 very well?

There are 60x /0.85s, but I think they'd be better off going to 100/ 1.25 oil.
Do you think it is advisable to use oil objectives in this setting? They are no easy to use and can easily be punched into the cover slip. It also takes some time to set the microscope up and clean everything afterwards. A school lesson would be very short to do this.

As such I don't think they would use compensating eyepieces.
Normally a 100:1 finity objective would be used with correction eyepieces. It is difficult to know what eyepieces there are and how they would work together with a new 100:1 objective without trying.

I'm not sure if theirs are DIN - I don't think it would matter.
What does DIN mean to you and why doesn't it matter?

What condensers do the microscopes have, do they have a fine adjustment, how powerful is the illumination?


Bob

[zzffnn]

ChrisR,

I think your application would be served reasonably well by cheap 100x NA 1.25 oil objectives. Many amateurs do not mind CA or SA that much, especially when used with regular brightfield and stained slides.

Depending on the 60x NA 0.85 objectives, some may not have much longer working distance than 100/1.25 and cover thickness requirement is much more restricted. Oil immersion at NA 1.25 is very tolerant with cover thickness, as you already know.

The only issue is that you cannot go back to 40/0.65, once 100/1.25 oil objective is used (and oil is not removed). You can only go back to up to NA 0.3-0.4 (no more than 20x objective) or so.

I do think it is nice to have near perfect parfocality. If your other objectives are 45mm parfocal (per "DIN" standard), then you should get a 45mm parfocal 100/1.25. You can shim about ~0.5mm or so at objective shoulder with a think rubber band some twisting force, but >1mm parfocality difference would be uncomfortable for most users, especially young children. I use oil immersion a lot more than other microscopists and don't mind oil, but I do always want near perfect parfocality.

[Hobbyst46]

...The only issue is that you cannot go back to 40/0.65, once 100/1.25 oil objective is used (and oil is not removed). You can only go back to up to NA 0.3-0.4 (no more than 20x objective) or so.
...
I do think it is nice to have near perfect parfocality. If your other objectives are 45mm parfocal (per "DIN" standard), then you should get a 45mm parfocal 100/1.25. You can shim about ~0.5mm or so at objective shoulder with a think rubber band some twisting force, but >1mm parfocality difference would be uncomfortable for most users, especially young children....

In my opinion, especially for children at school, and in favor of their teacher/instructors, these two important issues rule against oil objectives.

[75RR]

Another alternative would be to use higher magnification eyepieces.

There is a formula (well a rule of thumb really) to calculate this: Range of Useful Magnification (500-1000 x NA of Objective)

In which the 500 x NA (Numerical Aperture) is the minimum necessary for the detail present in an image to be resolved,
and anything over 1000 x NA gives empty magnification.

as an example:
For a Plan 40/0,65NA Objective
the range would be between
500 x 0,65 = 325 and
1000 x 0,65 = 650 so
below 325x total magnification, detail will not be resolved
above 650x total magnification, no additional detail will be resolved

best Useful Magnification Range for this objective is between 325x and 650x

A quick test is to multiply the NA of an objective by 1000,
then multiply the magnification of the objective by the magnification of the eyepiece,
if the second figure is higher then using that objective with that eyepiece will result in empty magnification.

Another useful test is to divide the max magnification by the objective's magnification, this gives you the max eyepiece magnification for that objective.
In this case 650/40 = 16. Therefore a 16x eyepiece would be ok (just) but a 20x eyepiece would give empty (too much) magnification with this objective.

[zzffnn]

Hobbyst46,

I don't disagree with you. It is safer to avoid high magnification objectives, unless teacher has full control or children are very disciplined.

I noticed, with my 8 year old son, sometimes he would do exactly what I told him not to do, again and again Things like don't hang his body weight onto microscope head, which is fine with my Nikon Optiphot (still not advisable) but would cause major damage with my LOMO Biolam (whose head moves, instead of stage, into focus).

[ChrisR]

Well,
the kids aren't young, teacher's in control.
An "A" level biology teacher asked me to see what's around and any opinions. Schools are normally limited to official sources and inflated prices. I got them a couple of haemocytometers for a tiny fraction of the regular supplier's price.
I don't know precisely what bit of what chromosome they want to view, but I'll credit the teacher with knowing what she wants to look at. Human ones are only a couple of microns.

Do you think it is advisable to use oil objectives in this setting? Well I do know the school/kids/technique.

I suggested oil because I find it much easier to use oil than a high-dry even with a collar, as Fan says. School coverslip thicknesses will be all over the place. It makes quite a difference at NA 0.85.
They woudn't need them a lot, but a couple would be good to at least try.

Normally a 100:1 finity objective would be used with correction eyepieces.Depends on the make/model. I believe more recent ones tend to be CF, like Nikon have been for a few decades.
Even the old scopes designed for Huygens eyepieces would be OK, I expect.

But New is better than cheap old, because they might want some more.

Good point about a say 15x eyepiece. I'm not sure what they have.

It's odd that I haven't got a "good" 100x biological objective, because I seem to have collected a bunch. But higher magnification than a 60/1.4 is empty on a camera.
I think I'll lend them an old Oly and see how they find it sans correction. I don't suppose a modern one would be much worse. The worst I've actually seen on a cheapie (20x) was a small image circle, it was ok in the middle.

[MicroBob]

Of the simple achromats the 100:1 is by far the most difficult to make. The Chinese can get this right but they have a tendency to get far easier things wrong so I wouldn't like to play quality control for them.
Do the condensers have an adequate n.a.?

In use I see these challenges to be mastered:

Time - it takes a while to set several kid up properly and to clean up after the lesson
Getting the focus right - As soon as the front lens is swung into the oil it doesn't help any more to look from the side, you can only hope the spring behind the front lens saves the cover slip if you are wrong. The depth of field is also very small so if you are not hafway right at the beginning you are in trouble Here parfocality is essential.

It is great that they do intensive microscopy with the kids and trust themselves to use oil immersion with them. You might set them up on one microscope and try to figure out how to explain the setting up to the kids. If this works well they can expand from this point.

Our microscopy group has set up a microscopy laboratory that we use for our meetings but that is also used for biology classes. We have our own microscopes but until a year ago we had to use the school microscopes when attendance to the meeting was especially good. To get an idea whether this really makes sense we checked two of the microscopes thououghly: The image of the 4:1 and 10:1 objectives were really ok, but both 40:1 objectives gave a dizzy yellow image. We cleaned them and found a yellow substance on them, probably pollen.

We ourselves never use oil immersion on the meetings though the members and guests are adults and most know their way around a microscope. It just takes up too much time and there is too little gain.

[photomicro]

As a Biology teacher of 30 years, I have been following this one with interest. Most of the following relates to the UK, which is where the school Chris mentions is, but some things are probably worldwide.

Once upon a time, when at A level (and below) organisms *other* than mammals and higher plants were on the syllabus, oil immersion lenses were more common. Apart from looking at chromosomes, they were used to look particularly at bacterial smears and blood smears. Over the years, as curricula became ever more narrow, there became less of a need, and indeed in time the experience in this area of the teachers themselves didn't include much in the way of the proper use of the microscope. As a mentor to PGCE students over many years, it has sometimes amazed me that graduates often claimed they had hardly used a microscope!

Some more practical questions/suggestions;

1. Not sure if Chris states if the chromosome slides are to be made by the students (ie. root tip squashes) or prepared ones. Most A level syllabuses require the former, but unless you spend a lot of time on them, they often don't produce very good results. There are some practical tips that can improve success. Keith Brocklehurst, a UK teacher who wrote O level textbooks that some of us were brought up with, made some excellent slides showing chromosomes, and I feel lucky to have several of these, mostly broad-bean and onion.

2. Prepared slides can be easier to use to see the various stages of mitosis or meiosis, however, the variation in quality is huge. Transverse section of roots are good, but modern makers, even well know names in the UK such as Philip Harris are often rather poor, with some of the older slides from the 1970s being better.

3. It is rather difficult to use oil, especially when a student with limited experience and time, with temporary mounts that would be made with squashed tips, but permanent slides, especially thin sections lens themselves more to this technique.

4. I am puzzled why they only need two lenses. Is this because they only have a few students, a few reasonable microscopes, or down to funding?

5. I have a Chinese objective set, that are remarkably good. However, it is difficult to distinguish one make from another, as they look very similar, and don't have makers marking on other than magnification, NA etc. I have to be honest and say I have never tried the x100. (*) I am unsure if they require correcting eyepieces by design, though suspect not.

6. I know it is stated the microscopes have critical illumination, but feel we need to know a bit more, especially of the condenser.

Hope this is of some help.

Mike

(*) if you want to get in touch Chris, I am quite happy to send you the x100 for them to try.

[ChrisR]

Thanks all.
My impression is that a couple would be OK, if set up by the teacher and the students came to the microscope, only allowed to use fine focus, or something like that.
They have to share microscopes as it is.
(When I first turned up there were three out of action, marked as "Dangerous?".
Intrigued, I was told that they were dangerous because they kept blowing bulbs or not working so there must be something wrong with them.
You know where this is going - some said 230VAC, some said 12V...)

The students aren't taught anything much about microscopy, but "oil used for....", gets a mention. They do an allium squash but practical time is severely pressured because the syllabus has gone nuts. Combined Science GCSE (age 16) counts for two subjects and is meant to be parts of the biology, physics and chemistry content. It has grown though, so seems to cover more than those used to, individually. The "less sciency" kids go for the double because it's less grunt than all 3 separately, but they're overwhelmed. There's a lot in biology which I think isn't really biology etc etc..

Yes they use here's-one-I-prepared-earlier slides.
I think the 16 year old group is OK at 40x, but a chromosome even of one of those hardly fills the frame, does it? Unless mine were shallots. The older kids(GCE A level) prompted the query - I'm not sure what for.
I'm only a volunteer teaching assistant. I don't do biology but I do get involved in take-it-slowly powerpoints for things like oxidative phosphorylation and some of the mathsy things where the materials are disgraceful.
I've got lots of things I could demo in physics but I was getting rebuffed. I pressed a bit, to be told that there's only one student (out of a cohort of 300) doing A level physics. Apparently that teacher thinks practicals are a waste of time.

Where was I...?
I've just looked at some Philip Harris scopes and see their cheapest have 0.65 condensers. I didn't know those existed - I assumed 0.9 if not 1.25 . If the school's are 0.65 , that would have a bearing on the 1.3's then!
I shall look again.

Maybe a 15x eyepiece with a dry 60x 0.85 would be worth a try.
Thanks for the offer, Mike, I'll let you know.

[MicroBob]

It is fairly easy to get a good microscope image on a full- HD screen. So it would be an idea to let the kids gain some practical experience with their microscopes with standard equipment and then demonstrate the few details where a 100:1 oil is needed on the teachers demonstration microscope. If there are kids who care about microscopy they can help with the preparations and do the demonstrating themselves.

For me the most important point to teach would be that it is possible for everybody to practically work on scientific tasks with just a bit of effort. So I would better do some preparation work like the onion tip sqashing and staining than spend much time on gettig them aquainted with the oilded "cover slip punch".

[apochronaut]

Thanks all.
My impression is that a couple would be OK, if set up by the teacher and the students came to the microscope, only allowed to use fine focus, or something like that.
They have to share microscopes as it is.
(When I first turned up there were three out of action, marked as "Dangerous?".
Intrigued, I was told that they were dangerous because they kept blowing bulbs or not working so there must be something wrong with them.
You know where this is going - some said 230VAC, some said 12V...)

The students aren't taught anything much about microscopy, but "oil used for....", gets a mention. They do an allium squash but practical time is severely pressured because the syllabus has gone nuts. Combined Science GCSE (age 16) counts for two subjects and is meant to be parts of the biology, physics and chemistry content. It has grown though, so seems to cover more than those used to, individually. The "less sciency" kids go for the double because it's less grunt than all 3 separately, but they're overwhelmed. There's a lot in biology which I think isn't really biology etc etc..

Yes they use here's-one-I-prepared-earlier slides.
I think the 16 year old group is OK at 40x, but a chromosome even of one of those hardly fills the frame, does it? Unless mine were shallots. The older kids(GCE A level) prompted the query - I'm not sure what for.
I'm only a volunteer teaching assistant. I don't do biology but I do get involved in take-it-slowly powerpoints for things like oxidative phosphorylation and some of the mathsy things where the materials are disgraceful.
I've got lots of things I could demo in physics but I was getting rebuffed. I pressed a bit, to be told that there's only one student (out of a cohort of 300) doing A level physics. Apparently that teacher thinks practicals are a waste of time.

Where was I...?
I've just looked at some Philip Harris scopes and see their cheapest have 0.65 condensers. I didn't know those existed - I assumed 0.9 if not 1.25 . If the school's are 0.65 , that would have a bearing on the 1.3's then!
I shall look again.

Maybe a 15x eyepiece with a dry 60x 0.85 would be worth a try.
Thanks for the offer, Mike, I'll let you know.

Having had a lot of objectives go through my hands , I have had the chance to see first hand what the differences are between those various objectives and the characteristics of various families of objectives.

Firstly, based on what you are indicating about your situation I would obtain one, 100X 1.25 oil immersion objective and have that available on one scope. If it is needed, it is there. I also might entertain sourcing a couple of higher magnification Lomo water immersion objectives. All, could be set up with parfocalizing adapters to match the objectives on the scope that carries them. The difference in any tube length won't make a sufficient amount of difference to be noticeable.

The Chinese objectives I have used seem to be of designs that go back to their intial introduction of D.I.N. optics, in the 1980's. There are a few of a more advanced manufacture and even some planfluor types but then they begin to be priced accordingly. For most of them ,the imaging is average but they don't have the best contrast. A bigger problem is the mechanical construction, which can be average to poor. I have come across several with very poor parcentering, to the point of having to search for the targeted sample, after dialing up from a 40X. This isn't such a problem for a seasoned user but for students it can be frustrating. Personally,if you were looking for a D.I.N. 160mm objective, I would opt for a Vickers Microplan or PZO plan D.I.N. 100X, which can be found at least as cheap as a new Chinese objective and both are far superior.
Here's a Vickers 100X 1.30 Microplan for about the price of a lousy Chinese objective, in Pontypool.
https://www.ebay.co.uk/itm/Vickers-Micr ... rk:33:pf:0


If you are considering a 60X dry objective of .80 or .85, the Chinese versions of those I have tested do not hold out much promise , either.
Here is a test I did for this forum. Note the results with the Chinese objectives. The 100X I have trialed , don't fare any better. You can't make a silk purse out of a sow's ear.
Unless you were aiming for an unusually high grade of 60-63X objective and a matching eyepiece with decent eye relief, getting into a 15X eyepiece would be problematical, although some options do exist. Again, I would search out the later D.I.N.Cooke-Baker or Vickers( they are the same). They should be reasonably well represented in the U.K.

viewtopic.php?f=5&t=4963&p=45168#p45168

[ChrisR]

Fascinating comparison, Apoc, thanks.
I was already looking at an objective, and the encouraging results from some of the old ones in your comparison made me buy it.
Ebay 273680123059, an old (30's?) Leitz Pol 100x 1.3 170
As it happens aI have a Leitx HM-Pol 170 scope.
It came with little, but now I have some bits and pieces. (Anyone got a wedge?!)

I assume "1/12th" is of an inch? Somewhere about right! (80x?)
The vendor assures me it's free of fungus and scratches on the glass.

The project onto screen idea is one I proposed when I first arrived. The teacher doesn't fancy one, and they don't have a suitable camera really. It's time to readdress that.

[desertrat]

I have an old Leitz 100x oil immersion objective that's also marked 1/12. That was a near approximation to the focal length in inches. In the early 20th century, the 1/12 designation was used on some oil immersion objectives where longer focal lengths by the same manufacturer were marked in millimeters, or some numerical identification was used that wasn't related to focal length. It was also used by American and I think some British manufacturers before the change to marking the focal lengths in millimeters.

[apochronaut]

Fascinating comparison, Apoc, thanks.
I was already looking at an objective, and the encouraging results from some of the old ones in your comparison made me buy it.
Ebay 273680123059, an old (30's?) Leitz Pol 100x 1.3 170
As it happens aI have a Leitx HM-Pol 170 scope.
It came with little, but now I have some bits and pieces. (Anyone got a wedge?!)

I assume "1/12th" is of an inch? Somewhere about right! (80x?)
The vendor assures me it's free of fungus and scratches on the glass.

The project ont screen idea is one I proposed when I first arrived. The teacher doesn't fancy one, but they don't have a suitable camera really. It's time to readdress that.

1/12" and 1/15" became commonly used focal lengths by many companies. Some are marked with a magnification as well, others not and you can find identical objectives often, just marked in mm. Oddly, continental companies continued to use imperial measure for objectives long after Spencer for instance had switched to metric; around 1895.
1/12" is just a nudge over 2mm and most 2mm objectives in a 160mm tube seem to run around 90X, so in a 170mm tube your objective will be around 95X.

[ChrisR]

Do you know how old it's likely to be?

[desertrat]

Do you know how old it's likely to be?

One of our members who has a lot more experience with Leitz objectives could give you a better estimate. What little I know is early in the 20th century Leitz was marking its objectives with numerical designations but no magnification marking. The 3 was 10X, the 6 was 45X, and the oil immersion, about 100X, was marked 1/12. My objectives from the 1930s are marked with both the numerical designation and the magnification. Later on, Leitz abandoned the old numerical designations, but I don't know when. Yours has both, and it looks like it was made after 1945, but I'm only guessing here. Also, somewhere along the way, Leitz abandoned the old 37mm parfocal length and went to a longer one. Mine are the old 37mm versions.

[apochronaut]

Do you know how old it's likely to be?

Do you know the serial #, Chris?

Rick. a 1930's Leitz 8mm, is marked 24:1 Extending that to a 2.1mm gives just over 90X. I thought I had a 1930's one marked 95:1 but I can't put my hands on it. 100X was not a default oil immersion magnification until the 40's at least. 100X would be a very high magnification for a 2mm 170mm tube objective.

[desertrat]

Apochronaut, My Leitz objectives came on a stand that I'm pretty sure was made in the 1930s. Of course, that doesn't mean the objectives are than old, but they look old.

The 1/12 Oel and the 6L (45x) are both plated brass, some of plating has worn off leaving the brass with a dark patina underneath. They both have two piece barrels that screw together, kind of like the antique brass Spencer objectives higher than 10X. These objectives were handled very heavily before the microscope was retired from service and wound up in the second hand section of a microscope dealer in San Francisco back in the early 1970s.

The serial number of the 1/12 Oel is in the 143,XXX range. The inscriptions are as follows. On one side:

1/12
Oel Immersion
Ernst Leitz Wetzlar

The other side is marked:

Apert
1.30
100X

The following images were taken quickly with the on board camera flash, so little of the inscriptions are visible:

Oel1.JPG (36.43 KiB) Viewed 10501 times

Oel2.JPG (40.27 KiB) Viewed 10501 times

This antique still gives a good image and works well on the 4 Series stand along with its siblings that came on the old Leitz stand.

[ChrisR]

100.jpg (41.41 KiB) Viewed 10496 times

171378
Only just noticed "Apert". Hope it works!

Looks a bit like the one on AO Pol here http://earth2geologists.net/Microscopes/LeitzScopes.htm

Well it was cheap, hoping the customs man doesn't stop it to add 50%.
50's cat

50s.jpg (70.51 KiB) Viewed 10496 times

1913 cat
The knurling is different:

1913cat.jpg (47.15 KiB) Viewed 10496 times

Looking at that cat it says 1.8mm FL and 105x

[desertrat]

I looked at the date chart, too, following the link you posted. I think that chart is for serial numbers on the microscope frames. The objectives may have used a different numbering system. I think your objective was made after WW1, perhaps after WW2. Hopefully one of our knowledgeable Leitz owners will post here.

My old monocular stand has a serial number in the 305,XXX range, dating it to around 1933. If the objectives are original to the stand, it would indicate objectives used a different numbering system.

The stand is also stamped Armstrong Coll. 7

I guess Armstrong College was where it was used before it was retired. There was an Armstrong College in Berkeley, California, which no longer exits. That was just across the San Francisco Bay from the store in San Francisco where it wound up and my parents bought it.

[75RR]

Given Cover Slip variation (especially so in cheaply made cover slips) I think every school lab should have a micrometer: https://www.ebay.co.uk/itm/Moore-Wright ... rk:20:pf:0

This Moore & Wright goes down to 0.002mm, which is what the doctor ordered.

A worthwhile donation, they are not expensive if bought used and when well made last forever.

[apochronaut]

100.jpg

171378
Only just noticed "Apert". Hope it works!

Looks a bit like the one on AO Pol here http://earth2geologists.net/Microscopes/LeitzScopes.htm

Well it was cheap, hoping the customs man doesn't stop it to add 50%.
50's cat
50s.jpg

1913 cat
The knurling is different:
1913cat.jpg
Looking at that cat it says 1.8mm FL and 105x

It's much newer than I thought it would be. The one I have has a serial # of 45898 with a brass upper section and plated lens section. It seems to be consistent with the objectives on microscopes in collections that are dated before 1910. Otherwise the specs. are the same. It is marked 1/12 oel immersion E.Leitz Wetzlar Apert. 1,30 on the upper brass section and 45898 on the lower plated section. I also have a newer one, looking more like yours but it only has : 100:1 oel A=1,30 made in Germany , so it was made before the German partition.

The two objectives seem very similar, except the one marked 100:1 has a slightly smaller front lens element, something usually associated with increased magnification.

[apochronaut]

Apochronaut, My Leitz objectives came on a stand that I'm pretty sure was made in the 1930s. Of course, that doesn't mean the objectives are than old, but they look old.

The 1/12 Oel and the 6L (45x) are both plated brass, some of plating has worn off leaving the brass with a dark patina underneath. They both have two piece barrels that screw together, kind of like the antique brass Spencer objectives higher than 10X. These objectives were handled very heavily before the microscope was retired from service and wound up in the second hand section of a microscope dealer in San Francisco back in the early 1970s.

The serial number of the 1/12 Oel is in the 143,XXX range. The inscriptions are as follows. On one side:

1/12
Oel Immersion
Ernst Leitz Wetzlar

The other side is marked:

Apert
1.30
100X

The following images were taken quickly with the on board camera flash, so little of the inscriptions are visible:

Oel1.JPG

Oel2.JPG

This antique still gives a good image and works well on the 4 Series stand along with its siblings that came on the old Leitz stand.

Quite interesting. Your objective is physically almost the same as my one, with a 45898 serial #. Have you tested it's magnification? There was I think a micscape article, published a while ago, in which the author presented tests of a bunch of older objectives and found most of them to have been rounded off, some quite a lot. This makes sense, because different glass batches would have differing qualities until the manufacturing obtained better consistency. Older objectives are usually shimmed in order to compensate for that but the magnification would vary somewhat.
Some companies stuck with the rounded off value, some changed their calculations in subsequent catalogues. Between 1914 and 1929 Spencer's 2mm apochromat varied from 82X to 90X, while the 4mm went from 40X to 44X.


I have two other 1/12 German objectives of a similar period of mfg. as the 1/12 E. Leitz. A C.Zeiss Homog.Immers. 1/12 N.Ap. 1.30 serial # 9412 and a Voigtlander Braunshweig 2mm n.ap. 1,30 Homog.Jmmersion 1/12 serial # 2403. Probably, at some point I will test them all for magnification. I still think 100X is pushing it for a 1/12 objective, even in a 170mm tube, unless the optical tube length (back focal plane to top of eyelens) is unusually long for a 170mm mechanical tube length which is more possible with a 37mm parfocal objective than say an older Zeiss 34mm. Voigtlander Braunshweig seems to be different yet, at 35mm.

[Hobbyst46]

There are 60x /0.85s, but I think they'd be better off going to 100/ 1.25 oil.

Hi, perhaps the following recent experience with my old, unknown brand (to me) 60X0.85 dry objective (marked only "60X 0.85") will contribute.
It is of 37mm parfocality. I attached it to the nosepiece by means of an RMS-RMS extender ring. Only the first turn of the extender thread is usable, and attaches the objective to the nosepiece. So, the total length of the objective + extender is 52mm and I used coarse focus to raise it above the cover slip. The WD is <~1mm, but, to my astonishement, focusing was not too difficult and the specimen was visible, though not very nice. The compatibility of the 60X0.85 objective with the photo setup is another question.

Here a 50 micrometer long diatom, where stria are separated by 1.1-1.2 micrometer, is observed with my 40X0.75 Neofluar (dry) and 60X0.85 (dry), respectively, in brightfield. The photos are resized and are much cropped. I feel that for secondary school students, a dry 60X would be an acceptable solution for objects measuring a few micrometers.

[ChrisR]

Thanks H46, I'll take another look at the microscopes, and confuse her with the options .