American Optical head fits Zeiss?

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GaryB
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American Optical head fits Zeiss?

#1 Post by GaryB » Thu Aug 02, 2018 9:17 pm

Hey all,

this may seem like a daft question, but do the AO heads fit Zeiss standards? I ask because I've seen these for sale attached to a Zeiss dual head block like the one below.

If this is the case, is the AO head standard 160mm-ish or is it an infinity head. I ask because my spare Zeiss frame is currently headless and the AO heads are much cheaper ~ $16 - 40 and It'd be great to get it back fully operational again. I'd even prefer infinity as I have some Lomo infinity objectives I'd like to play with.
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Scarodactyl
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Re: American Optical head fits Zeiss?

#2 Post by Scarodactyl » Thu Aug 02, 2018 10:21 pm

Looks like one of their infinity heads. (edit whoops guess not see next post) I tried one on my zeiss finite base and could not resolve an image.
Last edited by Scarodactyl on Fri Aug 03, 2018 5:23 am, edited 1 time in total.

apochronaut
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Joined: Fri May 15, 2015 12:15 am

Re: American Optical head fits Zeiss?

#3 Post by apochronaut » Fri Aug 03, 2018 12:11 am

That is a binocular from a series 2/4, so 160mm. AO never used metric measurements and only the occasional metric screws show up in them, so the actual measure of the wide part of the dovetail on that head is 1 7/8", or pretty close to 47mm. The infinity heads are 2" or 50.4mm.
There was a compensating optic in the yoke below those heads, which was both colour correcting and field flattening. The head therefore works better with that optic intact but nevertheless is a standard head made for a convergent beam.
The problem comes, in determining how much of the 160mm of the optical tube takes place in the head. It is sure to vary somewhat with each head design. In the case of that AO head there is around 55mm from the objective shoulder to the dovetail seat, and includes the compensating optic, so somewhere over 100mm takes place in the head and eyepieces.

GaryB
Posts: 77
Joined: Tue Sep 05, 2017 10:33 am

Re: American Optical head fits Zeiss?

#4 Post by GaryB » Fri Aug 03, 2018 4:16 am

Thanks for the info, guys.

Looks like I'll continue the hunt. I wish there were easier ways of finding out what heads were infinity. I see a lot of infinity Lomo and Jena objectives, and lots of heads, but no idea what works with what as there seems to be little useful info on the web regarding matching parts.

apochronaut
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Re: American Optical head fits Zeiss?

#5 Post by apochronaut » Fri Aug 03, 2018 1:43 pm

It isn't whether a head is infinity or not, it is how the objectives are corrected and whether the tube lens of the system is matched to the objectives.

Somewhere up the tube, is a telon lens that converts the image from infinity to convergent. The telon lens also might perform various other tasks, such as field flattening, peripheral colour correction. There could even be a magnification factor. If the telon lens in the head isn't optically "tuned" to what the objectives are producing, then the resulting image will need further correction. It would be possible in the eyepieces but swapping heads and eyepieces around is entirely trial and error.

The older AO infinity heads, they are pale grey as a modified Jentsch model, or dark grey, black and rarely off white as a Seidentopf model, all have a telon lens in the base which does a bit of correcting for the 34mm parfocal series objectives, as well as as converting the infinity beam to a convergent beam.
The newer ones, are off white Seidentopf types, with a telon lens compatible with the 45mm parfocal infinity corrected objectives. Although the two groups of heads do the same thing with their respective series of infinity objectives, and are physically interchangeable due a common dovetail, they are not optically interchangeable.

The newer AO head seems compatible with Olympus infinity corrected optics but due to a 20mm difference in the required tube length, Olympus objectives are magnified 11.1% more in an AO system. With AO and Reichert D.I.N. optics in an OLympus system, the reverse is true and there is a 9% reduction in magnification.

Zeiss infinity optics , I'm pretty sure require a corrective telon lens and have a very short tube length as well. 168mm or something like that. It would seem unlikely that using a different head designed for a different infinity system would work for Zeiss objectives.

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Crater Eddie
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Re: American Optical head fits Zeiss?

#6 Post by Crater Eddie » Fri Aug 03, 2018 3:30 pm

For a finite TL system I would suggest a LOMO viewing head as a likely match for a Zeiss scope. They are readily available, pretty cheap, and generally good quality. I have no idea about the Infinity systems though. You might get lucky, you might not. American Science and Surplus has or had a few Infinity type viewing heads for around $200. Worth a gamble?
CE
Olympus BH-2 / BHTU with Olympus E-P1 MFT camera mounted
LOMO BIOLAM L-2-2
LOMO POLAM L-213 / BIOLAM L-211 hybrid
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