Replacement aux lens for AO 34mm infinity scopes

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dtsh
Posts: 977
Joined: Wed May 01, 2019 6:06 pm
Location: Wisconsin

Replacement aux lens for AO 34mm infinity scopes

#1 Post by dtsh » Fri Mar 25, 2022 3:57 am

The aux is only necessary to deliver a fully illuminated field for the 4x and 2.5x objectives. Between losses due to many hands over many years and that the aux lens was an option, I ended up with a few condensers which were lacking one. It's not terribly hard to find another condenser with an aux, but then you end up overpaying and with a spare condenser that lacks it. So in my attempts to get more of the AO10 scopes off my shelves and into people's hands, I decided to try my hand at fabricating a replacement.

I was unwilling to risk destroying an original, so the dimensions are based off the original but adjusted to use the lenses I could find. I ended up settling on 29mm diameter lenses with a focal length of 25mm as it was a close match with the original. I don't know what type of glass the lenses are, but they are glass and not acrylic.

I went through a few iterations of the frame/holder, but am pleased with the appearance and function of the final result. I modeled the lug for the stop on one of the aux lenses I have with an oblong shape which allows adjusting the position for center, I don't think it's necessary as the variation among the condensers I have is negligible; about the only variation I have come across is that most of the condensers take a #2-56 bolt and an oddball or two that take a #6-40 bolt for the stop, both use a #6-40 for the pivot bolt.

It's hard to see, but there is a lens mounted in there! The lenses are a press-fit that's quite tight.
ao_aux_2.jpg
ao_aux_2.jpg (217.97 KiB) Viewed 2030 times
I only needed 2 of them, but ordered 4 lenses in case there were losses in prototyping, so I have 2 spares. If there's an interest in them, I would happily sell them with mounting hardware for $15.00/each including shipping to the continental US (can ship elsewhere too for the extra cost of shipping). If there's a surprising amount of interest I can share the files or buy more lenses to fill the need. If the two spares sell, I'll probably order more lenses to have as spares.

Here's an image from another angle so you can see the lens.
ao_aux.jpg
ao_aux.jpg (132.79 KiB) Viewed 2030 times
And here it is attached to the condenser.
ao_aux_4.jpg
ao_aux_4.jpg (138.94 KiB) Viewed 2030 times
I've had it in use on a 10 with a 1036A illuminator (17w tungsten) for several hours and there's not enough heat generated to deform the plastic. I don't have a working Series 20, so can't comment in regard to the heat it might produce at the condenser, but I would be surprised if it were enough to cause issue.

PeteM
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Joined: Tue Dec 06, 2016 6:22 am
Location: N. California

Re: Replacement aux lens for AO 34mm infinity scopes

#2 Post by PeteM » Fri Mar 25, 2022 7:18 am

Looks great.

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

Re: Replacement aux lens for AO 34mm infinity scopes

#3 Post by apochronaut » Fri Mar 25, 2022 10:52 am

Yes. Very nice job. Looks like it should work very well.

dtsh
Posts: 977
Joined: Wed May 01, 2019 6:06 pm
Location: Wisconsin

Re: Replacement aux lens for AO 34mm infinity scopes

#4 Post by dtsh » Fri Mar 25, 2022 4:03 pm

Thanks for the kind remarks.

It's not an impressive thing, but if you don't have one it makes the lower power objectives far less effective.
Here's an image taken through the eyepiece using a 4x Cat.1017 objective without the aux:
aux_flea1.jpg
aux_flea1.jpg (54.6 KiB) Viewed 1968 times
and here's one with it in place:
aux_flea2.jpg
aux_flea2.jpg (52.82 KiB) Viewed 1968 times

dtsh
Posts: 977
Joined: Wed May 01, 2019 6:06 pm
Location: Wisconsin

Re: Replacement aux lens for AO 34mm infinity scopes

#5 Post by dtsh » Mon Apr 11, 2022 5:32 am

Today I was using the 2.5x plan achro Cat.1028 objective and the replacement is just a bit too small in diameter and left a black edge to the field.
It works well for the 4x objective though.

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