Objective help.

[Placozoa]

I purchased a new objective for my premiere 160/DIN microscope. It was not parfocal, as I would expect, but it was so not parfocal that I cannot raise the stage high enough to get it to focus, even with the stage stop screw completely removed. If I put four slides under the commercial slide I was testing it with, it focuses fine and behaves as expected. I also have an amscope 160/DIN microscope and the same problem with that one, even with the stage stop screw removed. The objective is labelled 160/0.17 so it should be the proper objective. My question is, is there something wrong with the objective? Does it not really not conform to DIN standards or am I doing something wrong? I am new to microscopy, although I am quite mechanically competent.

[Placozoa]

In snooping around I noticed a reference to "short barreled" objectives. Could that be what this is? Are there adapters for them, if so?

[apochronaut]

D.I.N. objectives are 45mm parfocal, which means that a 40X objective will be just slightly under 45mm long from the objective shoulder to the tip. Many other parfocal lengths that are not D.I.N. as short as 32mm can slso have a 160mm tube length and be corrected for a .17 mm cover slip. I suspect you have confused the
160mm .17 specifcation as meaning that any objective with that specification is D.I.N. Not so.


You can use a collar to lengthen the objective but it will increase your magnification factor a little and in some cases the image quality is degraded. You need to know what parfocal length you have bought, so you can buy the correct adapter length.

[Plasmid]

Is there an LWD printed in the side of it ?

[Placozoa]

It states the magnification/N.A., then 160/0.17, and has a dark blue band. It does not state the working distance or anything else on it. I am reasonably sure it was sold as a DIN objective, and I am wondering what sort of a review to leave the seller (I bought it through amazon).
There are no microscope stores anywhere close to the city I live in, and very few people in the city even use microscopes. A few vetrinarians and an ecological research lab. All of our medical microbiology work is shipped out and the labs closed long ago. As a result I have limited sources and I am stuck with amazon or ebay and learning the hard way.
The new one seems to have a parfocal length of ~35mm and my other ones are 45mm. I was unaware this was a possibility, I mistakenly thought all objectives for a 160mm tube length (and labeled as such) with the proper threads were interchangable and would just require slight refocusing because they dont match the others.

[MicroBob]

Hi,
if you have access to a 3D-printer one of these : https://www.thingiverse.com/thing:4567179/files
might do the job. On ebay you may also find suitable adapters. Depending on the price of the objective it might be more economical to just buy one that fits directly.

Bob

[Hobbyst46]

D.I.N. objectives are 45mm parfocal, which means that a 40X objective will be just slightly under 45mm long from the objective shoulder to the tip

This is possibly a key to returning the objective to the seller since it is not as listed, If the eBay list explicitly stated that it is a DIN objective.
Note that "DIN" (or D.I.N.) and RMS are sometimes (erroneously) considered synonyms.

[MicroBob]

In this case it would be DIN 9345 that the objective doesn't fulfil.

[Charles]

It states the magnification/N.A., then 160/0.17, and has a dark blue band. It does not state the working distance or anything else on it. I am reasonably sure it was sold as a DIN objective, and I am wondering what sort of a review to leave the seller (I bought it through amazon).
There are no microscope stores anywhere close to the city I live in, and very few people in the city even use microscopes. A few vetrinarians and an ecological research lab. All of our medical microbiology work is shipped out and the labs closed long ago. As a result I have limited sources and I am stuck with amazon or ebay and learning the hard way.
The new one seems to have a parfocal length of ~35mm and my other ones are 45mm. I was unaware this was a possibility, I mistakenly thought all objectives for a 160mm tube length (and labeled as such) with the proper threads were interchangable and would just require slight refocusing because they dont match the others.

I would suggest you inform your seller of your problem and you wish for a replacement or return for refund.

[apochronaut]

China used a shorty objective in many of their microscopes before the 80's. They switched over to 45mm parfocal mostly by the 80's and partially due to their willingness to sell to the broader industry but they continue to make cheap shorty optics for their domestic school microscopes. I'm guessing you paid very little for the objective.

[Placozoa]

Im sorted, I made a mistake. I bought a 185 instead of a DIN objective, my own fault. I may get the proper tap and die and make an extension, or I might make one out of plastic somehow. For now I just propped my slide on top of another slide with some nuts sitting on it. Ruins my optics, but its an opportunity to experiment with some additional lighting. I gave the seller a good review since it seems to be my own fault. Thanks for the advice everyone, it was much appreciated!

[Hobbyst46]

On eBay there were Chinese spacers, made of plastic, but a seller named Crystal something, in Spain, was making them of aluminum for a reasonable price.

Edit: found it: micro_crystal, Calipo, Spain. A dependable seller of good quality adapters.

[Greg Howald]

I have had similar focussing problems after placing extension tubes in the light path between the body and head of the scope. It would not focus at 4x.
I just went to the hardware store and purchased an o-ring to fit over the objective threads. This lengthened the objective and focus was possible.
That can be an easy fix for under a dollar. Yes the magnification changes slightly.
Greg

[Placozoa]

I ended up ordering a parfocal extender through ebay. Then realizing afterwards that this is actually a blessing in disguise. I can get a complete set of 185 objectives, light my amscope microscope from above (the main lighting system is not great anyways), and this will give me the additional working distance I need to use this on thick opaque samples. Somewhat like a stereo microscope, only with more power and no 3D. So, I ordered more "wrong" lenses. The others are cheap anyways (lower magnification).
As a bonus, I also realized my darkfield filter was in the filter rack and should be behind the light source lens. Then I dont have to sacrifice anything because my darkfield filter and my diaphragm cannot both be in a focal plane if they are both between the lightsource lens and the stage lens.

[PeteM]

Sorry to say, your "185" objectives won't necessarily have more working distance (from the end of the objective to the specimen) - at least if you want them in focus.

[EYE C U]

ON A ZEISS I MADE UP THE THE GRANDKIDS I USED SKATE WHEEL SPACERS UNDER THE STAGE TO RAISE IT 10MM

[Placozoa]

@petem: the distance i want is from the end of the objective to the bottom of the slide. To observe soil organisms in situ I have to grow the plants next to a slide, or even better sandwiched between 2 slides. This leaves a paltry 7mm or so of dirt for the plants to grow in, which meant transplanting very quickly and with not much success. 17mm thickness will be a vast improvement, buying me enough time to make the transplanting more successful. On top of that, I also buy objectives with long working distances (N.A. and therefore resolution suffers) to be able to focus through a slide. (I could try a large coverslip, does anyone know if they are strong enough for that?). Observing the rhizosphere directly is worth it, imho, its a unique world, normally reserved for high end macrophotography.

[apochronaut]

What magnification are we talking about ?

[Placozoa]

The 4x objective has tons of working distance and so does the 10x. I would like a 20x also, and should a situation arise where I want to use my 40x or 60x then it would be nice. I think what I will do is order a pack of large coverslips, sandwich the sample (slide-coverslip-dirt/plant-coverslip-slide), then when I am observing I can carefully slip the top slide out only leaving the coverslip.
So to answer the question directly, I typically use 10x X 10x = 100x magnification, but I am going to upgrade that shortly.
My parfocal extender arrived today, works perfect and cost a whopping 10$. The advice on here is not going astray, its all coming together.