Complete AO 20 for sale.

[apochronaut]

I have nothing to do with this sale. I just happened to notice it. This is a complete AO model 20 set up for DF. It even has the cat. # 1014 iris equipped 100X advanced planachro objective. Everything is there including the transformer and dust cover.
As it sits it will provide 450X and 1000X DF : very good DF. Add a set of #182 15X eyepieces and you have 675X as well. I don't know whether it has a 20X objective but it is likely.
I also don't know if there is a BF condenser with it as well. If not, the correct cat. # 1088 condenser can be bought for very little. I have a couple of extras, if anyone wants one. 35.00.
That would then be a complete high quality BF/high resolution DF microscope for about 350.00, if you add in the eyepieces, condenser and shipping to the US. They are a really nice microscope to use especially with the 15X W.F. eyepieces.
It also looks like it may be a 5 place nosepiece which is a fairly rare and desirable item on those. Hard to tell but I think so and I can see the #1014 100X 1.25 planachro , a #1078 or 1116 45X .66 achro, a #1019 10X .25 planachro and at least 1 other objective , likely a #1017 4X .12 planachro in the pictures. On the backside there should be another objective if it is in fact a 5 hole but maybe not.

https://www.ebay.com/itm/204087122760?h ... GTR=1#shId

[PeteM]

It's a good price as well. By the time I got all the parts for a working one, it ended up over $500. These are old and heavy - but with a robust build quality unmatched by most anything new under $2000 -- and with truly excellent darkfield images.

[Phill Brown]

What light source did they use?
Are the bulbs still available?
Just asking as I have no experience of anything AO.
Is it a catoptric oil only condenser? Bright spot in the middle type thing?

[apochronaut]

It's a very common 100 watt halogen. I bought 10 for about 25.00 a few years ago. I'm only on the second bulb for the 20.
Bulb # is Philips/Osram Xenophot HLX 64625.

The DF condenser fitted in that is a # 214F , spherical oil. Very good condenser. They were the mainstay of DF medical assessments for 20 years between 1965 and 1985 in N.A.. It's probably got Syph. all over it. not.

[Phill Brown]

Same type used in the Watson Hilux, they rarely become available.
I'd be interested to see a full frame DF image with that condenser type with 4x 13.
An iris isn't a great advantage over a stop for 100x If setting up for oil DF.
A monocular with an eyepiece camera is an excellent budget option to get the most from the resolution available.
Definitely looks like a good starting point,
I'd probably ask about the 5 position nose and buy it just for that if I had an AO to fit.
I have a 6 position nose for the Watson system 70 but it's left on the prototype out of respect.

[apochronaut]

I think I have only ever seen one oil DF condenser with an iris and I think it was a type that used a common base with a BF condenser.
The 214FDF condenser has an illumination field of just under 1000 microns, so 20X is as low as it can be used and still cover the f.o.v. with standard eyepieces . For lower magnification DF AO offered several options.
DF stops fitted into the filter tray of the BF condenser
Using a phase contrast carousel with it's achromat phase condenser and pairing 4 , 10 and 20X phase objectives with 40 and 100X phase diaphragms.The 4X objective yields really good DF using the 20X phase diaphragm and the #1242 phase condenser unoiled.
Another toric cardioid phase condenser # 2172 was also available for use with 10X through 100X objectives for DF but not the 4X objective.

I don't have a lot of images taken through such a system. There are a few here taken 8 years ago that give you a rough idea of it's capability in phase and DF but all are 10X and up.There is a further link in the thread that takes you back to earlier phase and DF images. https://www.microbehunter.com/microscop ... f=6&t=2458.

Member Rod Nabholz has posted a lot of diatom images both using the AO infinity planachros, including the #1014 100X iris equipped objective in DF and older series 4 apochromats all using the 214F condenser. Those are definitely worth a look.

[Phill Brown]

Apologies, I was referring to an objective with a n/a above 1 with an iris vs a designated funnel stop.
Set up for oil DF is such that removing an objective and fitting a stop is relatively minimal
I have an oil DF condenser and oil also.

[apochronaut]

Highly corrected plan objectives require many glass elements, often filling the barrel. Towards the end of AO's 34mm barrel era, the #1029 100X 1.25 planachro had a rear correcting group above the back of the objective, sticking up into the nosepiece. They did offer a funnel stop for the # 1079 100X 1.25 achromat, which had the typical achromat lens pack down in the front of the objective but the only real option for the plan 100X was an iris.

Bausch & Lomb offered only a" funnel stop " for the 100X 1.25 Flat Field achromat which was in a fairly long barrel, close to a D.I.N. length but had it's rear group as a common lens group above the nosepiece. It is in essence about a 60mm parfocal objective system with the objective diaphragm, a flat disc diaphragm situated in advance of the rear lens group. The " funnel stop" was a replacement disc diaphragm with a smaller about .85 N.A. hole. It wasn't really a funnel stop but more of a disc stop but they called it a funnel stop. When they introduced the planachromat 100X 1.25 , they then offered one with an internal iris. The new design didn't allow the rear diaphragm to be removed.
I was able to do the same thing on a Reichert 63X 1.0 glycerin immersion by unscrewing it's rear diaphragm and replacing it with one from a trashed 100X Reichert objective from the same series. A 100X objective will always have a smaller rear diaphragm than a lower magnification objective from the same series.

[zzffnn]

I wonder why many infinity scopes don’t offer an iris immediately before the tube lens, so that all the objectives in the same system can share and controlled by that single iris?

I understand many ideas are theoretically possible, but difficult or expensive to implement, if that is the reason behind it.

[Phill Brown]

Highly corrected plan objectives require many glass elements, often filling the barrel. Towards the end of AO's 34mm barrel era, the #1029 100X 1.25 planachro had a rear correcting group above the back of the objective, sticking up into the nosepiece. They did offer a funnel stop for the # 1079 100X 1.25 achromat, which had the typical achromat lens pack down in the front of the objective but the only real option for the plan 100X was an iris.

Bausch & Lomb offered only a" funnel stop " for the 100X 1.25 Flat Field achromat which was in a fairly long barrel, close to a D.I.N. length but had it's rear group as a common lens group above the nosepiece. It is in essence about a 60mm parfocal objective system with the objective diaphragm, a flat disc diaphragm situated in advance of the rear lens group. The " funnel stop" was a replacement disc diaphragm with a smaller about .85 N.A. hole.

Thanks for taking the time as always for giving so much information freely.

[arb566]

Just a heads up, i believe that stand has the 1016 50X .80 oil iris objective not the 1014 100X. However the 1016 is a very nice objective especially in darkfield and with 15X eyepieces the 750X mag. means I rarely use the 1014.
I have a 20 as well and can certainly attest to the robust build quality.
I would definitely chat with the seller due to the complete lack of description details in the listing.

[apochronaut]

You're right. I need better glasses or a bigger screen or both. I would hope the unseen objective is a 1014 but unlikely the way they are arranged.
1014's are harder to come by but show up. The expected price has dropped too. The last couple of them I saw sell on ebay for about 150.00. A #1079 with a funnel stop, less.
Yes. Ask questions for sure. The microscope is still a good deal for someone wanting serious DF.

[JWW]

https://www.ebay.com/itm/194905609607?h ... R-7bx4XwYQ